Sizing systems

[Brier]

One bit of information that might be useful to you all is how much filtration media is required per pound of fish. I have more of an aquaculture background than an aquaponic back ground.

A good average per pound of fish is 20-30 square feet of surface area for bacteria to colonize on. I will use 25 ft2 for this example. Different filter medias have different ratios. You can look these up if you are building a bio filter, and size it correctly.

A 3 foot by 6 foot grow bed that is 12 inches deep filled with pea gravel( That seems to be what most people use) has a capacity of 18 cubic feet. One cubic foot of pea gravel has roughly 96 ft2 of surface area. This grow bed has roughly 1728 square feet of surface area. If we divide this by 25 we get roughly 69 pounds of fish. This number can vary depending on flow rate, temperature, and of course root mass from the plants themselves. But this is a great starting point. If you want to be conservative you might down size, and call it 50 pounds. So if you chose to grow tilapia, and your target harvest weight was 1.5 pounds, you should be able to conservatively stock 33 tilapia per 3x6 growbed. Once you have this formula, you should be able to adapt it to other medias, although I have not been able to find the specific surface area of Hydroton so far.
I hope this might be helpful for members who are trying to decide how many fish to actually stock. If anyone comes across specific surface areas of various medias, please post them here.
Here is a link with some info on specific surface areas of commonly used filter medias. http://www.russellwatergardens.com/Styl ... diassa.php (http://www.russellwatergardens.com/Styles/filtermediassa.php) Also if you purchase media from somewhere like Aquatic Ecosystems, they usually list the specific surface area, and you can use this formula to size your filter to your desired stocking rate, or your ultimate harvest goal.
Good luck guys! This sure is a lot of fun isn't it?

[Hotrodmike]

Matt
Very good write up for most anyone in AP . Everyone has to deal with how many beds and how many fish to match . Funny thing is my painter was at Russell's just the other week when he was on vacation . His dad makes the fake rocks for them .
Have A Kind Day
Mike

[rfeiller]

how do you calculate gallons of water per fish? how do you deal with a closed system in relation to the growth of the fish, hormon secretion, parasites and disease associated with crampted quarters? the only issues i've seen addressed are the nitrification cycle and the conversion of ammonia to nitries to nitrates with nitrosomas and nitrobactor bacteria. (many other types of bacteria also help in the process such as aeromonus) also as discovered with the living reef wet dry systems, the bacterial pulled nutrients from the water to perform their task such as calcium, coral is a good buffer and it also provided the calcium the large bacteria beds needed.

if you add fresh water to the system, what is the dilution factor and still be able to maintain sufficient nutrients for the plants. i use taro floating (gets about 4-5' tall) in the koi pond system to stabilize the system, it contains 2500 gals with 13 koi ranging from 18" to 36", all are about 4 yrs old and two yellow belly slider turtles (female 14", male 10" got them when they were the size of a quater 19 yrs ago, but then the system is also an open system. a closed system would never have allowed the growth of the koi or the good health that they have enjoyed.

richard

[jackalope]

As far as calculating the amount of water per fish, I've seen several 'rules of thumb' used ...... 3 to 4 gallons of water per pound of fish seems to be pretty much the norm, however, 1 or 2 gallons per pound of fish is used by some commercial production farms - that said, keep in mind that these farms have top of the line bio-filtration, water circulation (pumps that will change the water 4 to 6 times or more per hour), well water from pure sources, micron-sized solids removal, etc. Something that most of us can only dream about ..... water so pure and clean, you could drink it straight from the FT ;) (YUK :!: :!: ). So, you would want to size your fish/fish tank ratio accordingly .... IOW if you intend to raise 300 fry in a fish tank to market weight (1 to 1.5 lbs. whichever you prefer), you had better have at the bare minimum at least a 900/1350 - 1200/1800 gallon FT/GB combination of water alone (not counting the media).

Just my 2 centavos .....

[davidstcldfl]

Hi Brier, Great post....lots of good information. :D

Your right, seems like most people in aquaponics uses gravel of some form. Most seem to say, use 3/4 inch gravel, as it doesn't plug up, like pea gravel. (3/8 -1/2 inch)
Lots of folks add red worms to the GB's to help keep them clean.
I wonder how much of a difference there is in the surface area between the two sizes of gravel?

We have a guy in Orlando (FL) that makes and sells pvc ribbon.
Here's the info he gives....
1 CU. FT. APPOX. 143 SQ FT OF SURFACE AREA/2LBS OF MATERIAL
That seems like a conservative amount.....Aquatic-Eco says their ribbon has 250' per sq foot

[badflash]

You can also check my post:
Calculating your Bio-filter (http://www.diyaquaponics.com/forum/showthread.php?128-Calculating-your-Bio-filter)

[Brier]

Heck badflash, You had already posted nearly the same info. :D Well it is nice to have it written down a couple of times around here, as I assume that is one of the largest concerns of people starting their first batch of Tilapia.

Maybe The two topics could be merged, and even stickied if the mods saw fit?

[badflash]

Keep it in both places. You never know where folks go looking.

The biggest open question is how to figure how many plants to take up the nitrates & phosphates. Every plant has different needs, and it changes with the size of the plant.

[Brier]

Keep it in both places. You never know where folks go looking.

The biggest open question is how to figure how many plants to take up the nitrates & phosphates. Every plant has different needs, and it changes with the size of the plant.

Wow! if you figure a formula out for that I will be impressed. Maybe possible if we were all growing bermuda grass in our systems. :D

[badflash]

Check my signature. I think the complexity of the issue requires constant feedback. That would be the farmers shadow. Nitrates and phosphates accumulate over time. React to that.

[rfeiller]

the reason that i asked for the dilution factor is if there were any published information on the minimum levels of nitrates to be able to maintain aquaponics, since nitrates can be measured, the type of plant and quantity would not need to be known. nitrates are insideous as far as the health and growth of the fish is concerned, because the fish's gills are not destroyed immediately as with ammonia, people are not as concerned as they should be with the levels of nitrates. fish weakened by nitrates are much more prone to parasitic infestations.

[badflash]

Tilapia are much more tolerant to nitrates than many other fish. 50 ppm or more does not effect them.

[Brier]

Before I became interested in AP, my standard technique for nitrate removal was partial water changes, and a good test kit. I always tried to keep nitrates under 40ppm. If I was getting close to that number, I would do a water change. I am anticipating far fewer water changes with AP, but would still maintain that as a loose guideline. And of course if you are using tilapia, you have a bit more leeway, as they are very tolerant of poor water quality. I have even been told by a long term tilapia breeder that they can even withstand ammonia as long as it builds slowly, and they have time to adjust. Not that I plan to allow that to happen.

[badflash]

SRAC reports say that tilapia can handle nitrates up to 300 ppm, but only about .5 ppm ammonia long term. The problem with ammonia is that it spikes, and seldom rises slowly.

In AP you seldom if ever need to do water changes. The key is to never remove or add too much fish or plants at anyone time. Just like water changes, the 50% limit applies, and you are better off with 25% harvests.

[Brier]

Hey badflash, what is your experience with tilapia, and nitrite. I have always kept my tanks salted to help combat the occasional nitrite spikes on a newer system. I have always cycled with ammonia chloride, but usually for a couple of days after adding fish, i still experience slight nitrite spikes. I change water until it balances out. Well what do guys do in an AP system to avoid this, since salt is not good for plant growth? Do people sometimes keep AP systems salted at a minimal level, that won't affect plant growth. Bottom line is I like adding salt, I am concerned about not being able to salt an AP system. And also since tilapia are fairly tolerant of poor water quality, can handle small amounts of ammonia, and large amounts of nitrate, what is your experience with nitrite tolerance? I have read that they are fairly intolerant. But salt can combat this very well.. Thanks in advance.

[badflash]

I don't use salt. I like to start out with a really small bio-load and a good seeding of bio-active bacteria from a heathy established system. It has never been an issue for me. As the tilapia grow, so do the good bacteria.

[rfeiller]

pheromones, hormones are still not removed by plants or nitrification. have you all done any comparisons of growth of fish in open systems versus closed systems I have seen stunted tilapia M. i will not be using tilapia in my system but KOI. Tilapia would never cover their cost, much less the labor in raising them in a 20,000 gal system with the cost of utilities and such in the SF Bay area, which in a decent economy KOI will. (although we know the economy is getting much worse) i know that in third world countries tilapia are used as part of their bio waste water treatment systems, i never buy imported tilapia or at a restauarant.
certainly not trying to be negative by any means, i always feel a responsibility to whatever i am raising to afford it the best that i can within reason.

thanks for all of the information. i have garnered a lot from this forum in the short time that i have been a member.

Rich

[davidstcldfl]

Hi Brier, At another forum, it's common for people to use salt in their system. I added (very) little to mine.
I don't remember it's use, being linked to nitrate spikes. (?)
Mostly for the fish's film....I also read where the tilapia can deal with colder water, if it has a little salt, it also adds some trace minerals.
I understand, strawberry's can't stand any salt....I can't think of any other plants, right off hand.... that can't tolerate any salt....(?)

[rfeiller]

i didn't know that strawberries can't tolerate salt. the largest strawberry farms possibly in the country, thousands of acres are right on the pacific coast in watsonville, ca. they are bathed in moist salt air constantly. the sea air and fairly constant climate is why they do so well. that makes me curious. there are many cultivers that are not available to the general public, i know i have been unable to get any of their plants from the strawberry growers that sell plants to the farmers. stuck with quinolts (sp) and other strains as old as i am.
isreal is a people that has done wonders with salt tolerant plants. what do they do?

years ago Jungle Products main ingredient in their meds was nothing but table salt. there are those that believe salt will keep the parasite levels down in their overcrowded fish habitats, of course it doesn't. the parasites adapt very readily to enviromental changes.
since freshwater fish use osmosis to transfer water and waste in their tissue cells, i can't beileve salt is all that great. i do like it on steak and eggs and the doc says none of that is a good thing. :-)
epsom salts is another thing; i found it be benificial for my fish that showed signs of shock. not to mention rose bushes.
rich

[Hotrodmike]

Rich
You have to keep in mind terms ! Every mineral technicaly is a salt . I could be off on this one but it may have something to do with table salt being Sodium Chloride and to make it you add chlorine to sodium . Sodium is not a problem but chlorine is .Also in most of the salt there is added iodine unless you use natural sea salt . Table salt is antibacterial so I can see the reasoning behind using it as a safe method of treating fish .

Epsom salts are Magnesium sulfate so not even close to what we call salt .

Basicly I think the fish can take a lot higher PPM of salt that most plants could and I did not know strawberries would not deal with ANY salt eihter but then I never salt while I water the garden ,so what do I know :D
Have A Kind Day
Mike

[Brier]

http://www.aces.edu/dept/fisheries/aqua ... /462fs.pdf (http://www.aces.edu/dept/fisheries/aquaculture/pdf/462fs.pdf)

Good reading on benefits of salt. Can help a system, especially early on when nitrite spikes are likely, or when adjusting populations.

I will without doubt still do water changes out of habit on my AP system, though less frequently. I would think 10% weekly would be a good idea just to keep up water quality.

[davidstcldfl]

I went searching and found some 'random info' on salt.....

-DON'T use table salt....iodine and anti-clumping agents are not good.
-1 lb per 125 gals = 1 ppt
-1 ppt (part per thousand) is very common, up to 3 ppt.
-1 ppt 'does' help with nitrate spikes. * see Brier's post above, he must of added that while I was off reading.. :oops:
-strawberries 'are' the most sensitive to salt...read 1 or 2 people, growing with 1 ppt...most say use 'no' salt for strawberries.
-plants will 'use up' the salt...someone mentioned spinach sucks it up...tomatoes like some too.
-adds trace minnerals
-using a Salinity Refractometer is 'one way' to measure salt....they said one can be picked up on Ebay, for not too much. Look for one that reads in 'ppt'
-helps with the slime coat on fish
-helps fight some fish diseases (sorry, I didn't write down which ones )
-depends on your fish, as to how much salt they can benifit from...
catfish needs to have a low ppt (1-2 ppt)...where as tilapia, can go (much) higher.

[Brier]

I use kosher salt. Nothing but salt. Many guys use stock salt from farm supply stores. My Tilapia in the house are kept at 6 parts per thousand. I have always used it, especially when fish are stressed, or when transporting them. Personally I think it is a great prophylactic treatment. So it sounds like I can still get away with using small amounts. Thanks guys.

[rfeiller]

I do know the chemical differences, thought that if a fish is stressed knowing aboutl Epsom salt could be of benefit to someone. Because an animal can tolerate something and even sensitive rainwater fish an tolerate.

[rfeiller]

Droid phone limitations
tolerating something doesn't mean it is a benefit. Much of the info today goes back to the dark ages of fishkeeping. There are better ways.
rich

[Brier]

Rfeiller, what is your common practice of water change? I am sure that there is a happy medium between keeping fish healthy, and happy, and being economical when it comes to water usage. In most of the aquaculture industry, I would venture to say that water is 80-90% recirculated. At least in recirculating systems. Flow through is a different animal. You are correct about hormone buildup (hence the old adage that a fish will only grow as large as it's tank allows), and also nitrate buildup. Both will stunt growth. Now with AP, nitrate should be a non issue if done properly. As far as hormone removal, if you are concerned, then obviously you will need to do regular water changes. Small frequent water changes will keep nitrate levels in check in recirculating systems. How much dilution is required to reduce hormones to a level that they become a non issue, I am not sure. I am not aware of any studies, but surely some have been done.

I would assume that 90% recirculation is removing enough of the hormones, as many of these aquaculture facilities are realizing fantastic growth.

Found this about koi. Sure you have read it.https://koistuff.com/shoppingcart/pages ... rowth.html (https://koistuff.com/shoppingcart/pages/Koi,-Hormones-%26-Growth.html)

[rfeiller]

brier,
my question was where is the ratio that would be the closest to the best of both worlds.

aquaculture/aquaponics (the efluent produces aldae and vegatation that aids in the "purification process" runs the gambit from a total open system such as is practiced in third world countries for processing sewege with the talipia being in the final ponds with the effluent going out for use by people. to the other extreme of total recirculation utilitzing dehumidifiers to remove the excess humitity in the air and returing it to the aquaponics system counting on the nitrification beds for the conversion from ammonia to nitrites to nitrates and counting on the fish to remove the nitrates. of course some de-nitrification transpires in the nitrifying bed as an anarobic process.

i would never without the use of nano filtration, GAC, resins, RO, ozone and uv ever have a total closed system, however i am looking for a place that i can feel satified with the results knowing that both ends of the process are a compromise, but acceptable.

the effluent from the system goes to watering the container and yard plants.
i am hoping for a target to base the system on knowing that there is a lot of trial and error.

Brier, as far as water changes it is a minimum of 10% per day for the koi set up i have now of 2500gals. the koi pond system under construction and will be finished in the spring is 20,000 gals.

sure appreciate the help

rich

[rfeiller]

by the way Brier, that was a good article, thanks for the link. i started working with ornatmental fish in the 60's while in my teens. these conclusions were drawn over 40 years ago, when the common practice was "aged" water in the aquariums. this aged tank conditions are what created so much of the information today about water changes, rust, iodine and so much more. maybe that is why i was breeding Discus when the publications said it was near impossible to keep them alive much less get them to breed.
immune system and fertility problems, not to mention the health of the animals that are being produced.
by the way this is fun, take a couple of tilipia m. and teach them to go through mazes and ring bells for their food, they are quite intelligent fish, at least the wild caught ones were. i played with a couple of them in 1972. they are a kick.


take care

Rich

[Brier]

Rich, for me most of 72 was a blur. Actually, that very year I was hitching a ride in my mom's belly. :D I wish I could answer your question, but you already know the answer. Frequent water changes are undoubtedly better for your stock. When I was raising lots of fish in aquariums, I had many of my tanks rigged with overflows, and I trickled straight tap water into them. It was such a small amount, only 5-10% per day, that I didn't even worry about dechlorination. These were my healthiest tanks.

I really think you will need to experiment with this to find out what is optimal. But with 20,000 gallons, I suspect you need to find the bottom range of optimal, for the sake of your pocket book. I am really interested in hearing what you come up with, and I will keep my eyes peeled for any info that might be of interest to you.
Matt

[urbanfarmer]

Some fish cannot tolerate any salt. Some breeds of Tilapia can tolerate seawater concentration levels of salt (roughly 35 ppt). Most Tilapia can survive brackish waters if they are slowly acclimated to the salinity (I have read studies of up to 20 ppt for nile and blue Tilapia if I recall correctly with a low mortality rate).

The reason salt helps with nitrite spikes is because the Cl- or Chlorine ions helps offset an imbalance caused by nitrite ions and the diffusion of ions through the gills of fish for their metabolic pathways. Nitrite spikes can cause brown blood disease or something like that... I forget now, but I think I was reading a SRAC article or something late one night...

As far as what rfeiller has mentioned... I know that some fish release growth inhibiting hormones into the water. As the concentration increases (because of the lack of water changes) the fish tend to stop growing and eventually die. In my days researching Tilapia, I have NEVER come across a fact that states Tilapia produce this kind of hormone. Where I have mainly seen this problem cited in studies, it has done with home aquariums and indoor aquaculture with recirculating systems. Why? Probably because a hormone or protein released into the WATER is easily broken down by the UV rays from the sun (or even better a UV clarifier), obviously, since it no longer belongs to a living organism that might aid in its repair or reconstruction... so, with those 2 things said, I doubt anyone, anywhere, would ever need to do "water changes" to prevent stunted fish growth... If you find some studies or references to the contrary, I implore you to post them! Thanks. :mrgreen:

P.S. Can you post on the economic feasibility of raising Koi for profit? I am trying to figure out what route to go as far as making a few bucks on the side with my soon-to-be large backyard aquaponic system!

[Brier]

It is common knowledge in both the aquarium hobby, and the aquaculture industry, that lack of water changes stunts fish growth. Try your own experiment keep several fish in an aquarium, and don't change water. Duplicate the aquarium, and change water. Even use tilapia, and a UV sterilizer. You will likely change your mind.

[urbanfarmer]

Oh, I see. Well, I am still learning, and I will try the experiment you propose once I get some fish and post my data and observations here with pictures! :ugeek: But for now, I will take your word for it while doing some more research on how to combat this issue. And yes, I have seen this first hand with the comet goldfish I have been raising. The ones in the pond outdoors grow much faster than the ones in the tank indoors even though I feed the ones indoors substantially more than the outdoor ones in a big pond.

I would like to point out that mathematically, it makes more sense to spread your water changes to as much water at any given time to be as much water volume at those given times as possible because this increases the effectiveness of the water changes.

For instance, assuming a fixed level of concentration of pheromone in the water at variable levels of water changes:
Given: P in units of pheromone per total volume of water

Where X equals the number of water changes over a fixed interval of time and C(x) equals the concentration of pheromone:
C1(x) = P x (0.9)^X
C2(x) = P x (0.8)^(X/2)
C3(x) = P x (0.7)^(X/3)

We want C(x) to be the lowest, and we find that at any given value of X: C3(x) < C2(x) < C1(x)

What I have done is model formulas that change the SAME AMOUNT OF WATER just spread over less frequent water changes. What the models indicate is that instead of changing 10% water daily, it is more efficient and less labor intensive to change the water 20% every other day, or 30% every 3rd day, etc. Of course, one must consider the effects of the water change on the rest of the biological system, but from a pure pheromone reducing perspective, that's the best solution.

[badflash]

All things take time. If you have a mature ssystem with lots of hungry plants, there is no need for water changes. Just add make up water and check your chemistry. Don't over harvest plants or fish once you strike a balance.

[urbanfarmer]

All things take time. If you have a mature ssystem with lots of hungry plants, there is no need for water changes. Just add make up water and check your chemistry. Don't over harvest plants or fish once you strike a balance.
but, what about their claims that there are eventually high concentrations of pheromones released by the fish to inhibit growth??

[Brier]

The pheromones are a factor, but nitrate build up is a much larger factor. This is where keeping fish in tanks, and aquaponics differ. A balanced system should eliminate the need for the frequent water changes needed in aquarium raised fish, or aquacultured fish.

The fish in you outdoor pond are likely growing better because of less nitrate concentrations. Your pond is not unlike an aquaponics system. You probably have some plants. Either intentionally planted, or some form of algae. Both will remove nitrates, and allow for better fish growth. Also the larger volume of the pond will help lower concentrations.

If you get a test kit, and test your indoor comet tank for nitrate, you might be surprised at the nitrate levels. Under 40 is considered optimum for most tank fish.

With my indoor tilapia in non aquaponic systems, I recently got lazy, and skimped a bit on water changes. I actually noticed that the fish became lethargic, and less aggressive at feeding time. Nitrite, and ammonia were fine, but nitrate was over 80. After a large water change, the fish were much more vigorous.

[badflash]

With tilapia, the phermones seem to restrict breeding, but not growth.

[urbanfarmer]

With tilapia, the phermones seem to restrict breeding, but not growth.
I am inclined to believe you, but I have genuinely not seen research either way. A few people here hold to the idea that it does affect the Tilapia's growth rate. I have only read studies where it affects breeding habits. However, I know some fish do release some kind of waterborne hormone, protein, or other biochemical as a survival mechanism that inhibits the growth of like species (intentionally or not). Even in the book "Tilapia: Biology, Culture, And Nutrition" he mentions (I think it was page 363) that he SUSPECTS there is some kind of waterborne substance that inhibits the growth of Tilapia at high concentrations, but makes note that he has no research to support that claim. Perhaps in the half decade since that book was published, there has been new research that might provide a reference for all of us? I don't know... but I'm hoping you do! :D

The implications are pretty huge if there is a waterborne substance that Tilapia release or indirectly cause a buildup of in the system that cannot be removed by existing filtration thereby causing growth inhibitions of our fish. Agree? :?:

[badflash]

I've not seen any stunting with densities up to 1 lb of fish per 5 gallons of water. The fish definitely self limit breeding.