What would you do?

[wh33t]

Ok, so I'm having some troubles with my system lately and I can't seem to figure out what I should do next. So I thought I'd see what you guys think.

Imagine this:

Your goal is to start Aquaponic veggies indoors that will later on be transplanted into an outdoor (green house). The outdoor environment will be a series of flood and drain systems in 3/4" gravel with bell siphons. The outdoor fish to start will be gold fish and later on some kind of edible variety, probably Talapia. The kinds of veggies will vary in range from Tomatoes to Strawberries.

So for the indoor portion of it here is what you have.

90 gallon raised pond on casters.
4x8 flood table that is built to drain into the pond.
Big water pump (I think it's an 850gph)

Please tell me what you would do in such a scenario.

[urbanfarmer]

I would use gravel instead of hydroton in the biofilter because it's a) CHEAPER and b) has more surface area.

Anyway. I'm not sure I understand the question. WHERE are you stuck?

The only other thing I would add is make sure that when you plant the initial seeds indoors, try to have a container that can flood but restricts root growth inside a container that can be removed once transplanted. An old pudding cup for smaller plants with a very small hole in the bottom and a few more holes in the top would do it. Consider the plant size and the amount of time it would be indoors, etc.

[wh33t]

I would use gravel instead of hydroton in the biofilter because it's a) CHEAPER and b) has more surface area.

Anyway. I'm not sure I understand the question. WHERE are you stuck?

The only other thing I would add is make sure that when you plant the initial seeds indoors, try to have a container that can flood but restricts root growth inside a container that can be removed once transplanted. An old pudding cup for smaller plants with a very small hole in the bottom and a few more holes in the top would do it. Consider the plant size and the amount of time it would be indoors, etc.

I didn't bother to explain where I'm stuck because I just wanted some fresh perspective on what the more experienced would do.

Currently though I've been having problems with my PH continually plummeting and what I believe to be root rot taking hold in the table which I attribute to the high build up of solids that accumulate in the table.

And thank you for the tip about the roots growing into containers. I never thought of that.

[urbanfarmer]

Try to see if you can add oxygen to those problem spots. It might clear everything right up for you.

[keith_r]

do you have composting worms in your bed? they really do assist in solids breakdown, and love being in the roots
buffering your ph with a long term solution is to add a sock or two full of shell grit... this will slowly bring your ph up... my system has been pretty stable at 7.2 after the first ph drop and subsequent addition of shellgrit

[wh33t]

Try to see if you can add oxygen to those problem spots. It might clear everything right up for you.

I added 2 air pumps that each have 4 air outlets each and spread them through out the flood table with little air stones. It kind of helped the plants a little that were in there but they were responding too slowly and I felt they would surely die so I already transplanted them into little soil pots so I could keep them alive. Mostly just lettuce plants though and it's all an experiment so no real harm done. But I would like to get this working. When the table is fully flooded and begins its drain cycle it's only 4 inches deep... A far cry from "deep" water culture so the air stones don't appear as useful as they would if the table were deeper.


do you have composting worms in your bed? they really do assist in solids breakdown, and love being in the roots
buffering your ph with a long term solution is to add a sock or two full of shell grit... this will slowly bring your ph up... my system has been pretty stable at 7.2 after the first ph drop and subsequent addition of shellgrit

No, my "flower bed" has no medium in it. The plants sit inside rockwool cubes, inside of a net pot with hydroton clay padding them which are then suspended in foam lids, so the roots actually just float. When the table floods they roots are submerged in water, when the table drains the roots are exposed to the air for about 5 minutes.

I do currently have this big gravel "particle" filter which I made which does have a few worms in it but it didn't seem to make a difference. There is still fine particles of fish waste that collect in the bottom of the flood table which collect together to form bigger clumps and then sooner or later the plants roots grow into these clumps and I think that is when the problem of root rot begins. My theory is that the anaerobic bacteria are much stronger in the table where the fish waste settles, that's why we added the air stones.

I should also note, I used to have 90 gold fish in this system. Someone informed me that I should have 3 gallons of water volume for every 1 inch of gold fish. So Now I have about 11 gold fish. They went to a good home though :) (a friends new tank)

[keith_r]

there are many threads on stocking densities... filtration is the key..
quite a few threads discussing this, but don't use the inch/gallons rules of thumb

[urbanfarmer]

there are many threads on stocking densities... filtration is the key..
quite a few threads discussing this, but don't use the inch/gallons rules of thumb
Yes, inch-to-gallons is absolutely a terrible "rule of thumb". How was this derived I wonder? Can you say a 10 inch fish is 10x more massive than a 1 inch fish or is the difference in mass far more substantial? Indeed, it is. From that example alone you can see how the inch-to-gallon concept breaks down instantly.

We usually try to simplify it by unit mass of fish per unit volume of water, but even this is oversimplified and often inaccurate. HOWEVER, this is a good starting point for a hobbyist because you can monitor your system closely and the potential loss is practically 0 in all cases.

Have fun, enjoy! :mrgreen:

[wh33t]

there are many threads on stocking densities... filtration is the key..
quite a few threads discussing this, but don't use the inch/gallons rules of thumb
Yes, inch-to-gallons is absolutely a terrible "rule of thumb". How was this derived I wonder? Can you say a 10 inch fish is 10x more massive than a 1 inch fish or is the difference in mass far more substantial? Indeed, it is. From that example alone you can see how the inch-to-gallon concept breaks down instantly.

We usually try to simplify it by unit mass of fish per unit volume of water, but even this is oversimplified and often inaccurate. HOWEVER, this is a good starting point for a hobbyist because you can monitor your system closely and the potential loss is practically 0 in all cases.

Have fun, enjoy! :mrgreen:

I'm not having issues with keeping my fish alive. I'm having a problem keeping my plants alive. If the "inch of fish per gallon" is a poor system of measurement what would you suggest? What about adding/removing fish until the nitrate levels are at 40ppm? or something to that extent?

[urbanfarmer]

No, the nitrates are fine. Flood and drain grow beds rarely have problems with oxygen, but you mentioned root rot... The correct way to calculate the required gallons and relevant surface areas is tedious and unless you already have an understanding of it, it's really too much to post here. Stick with the general "pounds per gallons" and "square feet grow bed per pound" rules of thumb provided by Oliver. The rest will be trial and error for most folks, which is part of the fun; so, enjoy it!

Anaerobic bacteria would cause denitrification, which causes an increase to your pH: 6NO3- + 5CH3OH => 3N2 + 5CO2 + 7H2O + 6OH

Anyway, the shell grit in a removable bag of some sort a great suggestion to adjust the pH problem. Not only will it bring it up, but it will allow the solution (water) to buffer itself.

[wh33t]

No, the nitrates are fine. Flood and drain grow beds rarely have problems with oxygen, but you mentioned root rot... The correct way to calculate the required gallons and relevant surface areas is tedious and unless you already have an understanding of it, it's really too much to post here. Stick with the general "pounds per gallons" and "square feet grow bed per pound" rules of thumb provided by Oliver. The rest will be trial and error for most folks, which is part of the fun; so, enjoy it!

Anaerobic bacteria would cause denitrification, which causes an increase to your pH: 6NO3- + 5CH3OH => 3N2 + 5CO2 + 7H2O + 6OH

Anyway, the shell grit in a removable bag of some sort a great suggestion to adjust the pH problem. Not only will it bring it up, but it will allow the solution (water) to buffer itself.

What do you mean the Nitrates are fine? I was asking if the nitrates are a good way of measuring the health of the system. If you have lots of nitrates in theory you would lots of fish waste right?

Currently I must not be experiencing dentrification because my PH keeps lowering steadily.

Also, I have shell grit in my system. As well as organic free range egg shells. They sit in my particle filter in the gravel from my drive way.

[Larry Dietz]

What kind of gravel do you have in your driveway?

I know around here, gravel driveways tend to be crushed granite and limestone. Either of these I would expect to steadily raise your PH.

I dont know of any type of stone that will push PH down, off the top of my head, but it might be something to look at.
Sorry if I am way off base here, but when I saw "gravel from my driveway" it just stood out.

Also, did you make sure to clean that gravel fully? Stones in a driveway tend to become contaminated with all kinds of things that are bad for both plants and fish.

-Larry

[keith_r]

if your ph was dropping before adding the buffers, i'd think that the media was ok..
the buffers should do the trick, but you may need to add a little more..
high nitrates are usually only problems for fish over 3 or 4 HUNDRED... but a balanced system should have them lower..get more plants in to use them up

[wh33t]

What kind of gravel do you have in your driveway?

I know around here, gravel driveways tend to be crushed granite and limestone. Either of these I would expect to steadily raise your PH.

I dont know of any type of stone that will push PH down, off the top of my head, but it might be something to look at.
Sorry if I am way off base here, but when I saw "gravel from my driveway" it just stood out.

Also, did you make sure to clean that gravel fully? Stones in a driveway tend to become contaminated with all kinds of things that are bad for both plants and fish.

-Larry

The gravel is crushed up 3/4" stuff. I'm not sure what kind of rock it is exactly but it looks like the very typical kind I've seen in many other peoples Aqua systems including Murray Hallams. I did clean it for quite sometime, but now that I think about it I'm not sure if I did clean it all that well. At any rate, the problem in the system is root rot and I'm not sure contaminated gravel would increase such a thing. But it might be something I have to look into after.


if your ph was dropping before adding the buffers, i'd think that the media was ok..
the buffers should do the trick, but you may need to add a little more..
high nitrates are usually only problems for fish over 3 or 4 HUNDRED... but a balanced system should have them lower..get more plants in to use them up

I can't put more plants in, they die from root rot and slimes and such on the roots. So far I have taken away a bunch of fish though and now I'm trying to be patient and see if the system will come back into balance.

[urbanfarmer]

I was asking if the nitrates are a good way of measuring the health of the system. If you have lots of nitrates in theory you would lots of fish waste right?
No.

[keith_r]

you're way overstocked..you have to much waste going into the growbed if you're experiencing root rot.. as uf said, try to get an air stone or two in trouble spots.. add composting worms to assist in breakdown of solids in the growbed/gravel - they'll be fine submerged as long as you have good DO
a good starting point for hobbyist/backyard aquaponics systems stocking density is 25 lbs (grown out size) for every 100 gallons of filtration..
so 25 fish you plan to grow to 1lb for every 100gal of gb

[wh33t]

Yes, I had a feeling I was over stocked for some time. Now I have about 1/10th as many fish and I painstakingly last night cleaned my entire flower bed out. I put all of the heavy solids into the compost :D We'll see what the plants in there do now.

[keith_r]

some worms will help in the growbed, red wigglers can usually be found at bait shops

[wh33t]

some worms will help in the growbed, red wigglers can usually be found at bait shops

I don't think they will as my grow bed doesn't have any medium in it. Just water. I do have some big fat dew worms in my heavy particle filter though. If they are making a difference I haven't noticed it at all yet.

[urbanfarmer]

some worms will help in the growbed, red wigglers can usually be found at bait shops
Any detritivores can help if they are in large enough quantity. I forgot the name... darn, I will post if I remember to, but they were small shrimp like ones that actually swim around and typically latch on to the roots and eat up all the decaying organic matter. They have had good results, and we have it in our system in Nicaragua with some of the plants that are only floating in water. The Friendly's also use these critters... darn I can't remember the name...

[keith_r]

do you mean gammarus? or scuds..

put the worms in with your hydroton.. if that is flood and drain using a syphon, you can certainly put plants in it,, just make sure that the water doesn't "flood" over the top of the hydroton
i thought you had media in your "grow tray" as well.. but now that you said it's just a flood table, add an air stone to it...

[urbanfarmer]

do you mean gammarus? or scuds..

put the worms in with your hydroton.. if that is flood and drain using a syphon, you can certainly put plants in it,, just make sure that the water doesn't "flood" over the top of the hydroton
i thought you had media in your "grow tray" as well.. but now that you said it's just a flood table, add an air stone to it...
gammarus!!! :D

[wh33t]

some worms will help in the growbed, red wigglers can usually be found at bait shops
Any detritivores can help if they are in large enough quantity. I forgot the name... darn, I will post if I remember to, but they were small shrimp like ones that actually swim around and typically latch on to the roots and eat up all the decaying organic matter. They have had good results, and we have it in our system in Nicaragua with some of the plants that are only floating in water. The Friendly's also use these critters... darn I can't remember the name...

Are they kind of like micro-shrimp? Daphnia? I really wanted to put some crayfish in the bed but I was worried they would munch the roots.

[wh33t]

do you mean gammarus? or scuds..

put the worms in with your hydroton.. if that is flood and drain using a syphon, you can certainly put plants in it,, just make sure that the water doesn't "flood" over the top of the hydroton
i thought you had media in your "grow tray" as well.. but now that you said it's just a flood table, add an air stone to it...

There is hydroton in the net pots which house the rock wool cubes. The roots grow out of the net pot into the flood table and the net pots are suspended in the air via some big styrofoam lids (not really styrofoam, polystyrene or something).

I put air stones in, unfortunately they didn't seem to help much. The PH still dropped dramatically but now that I've physically removed the excess fish waste that has accumulated in the system the PH appears to be steady at 6.2. So I think I'm getting there. I think the mistake I made was that I was too impatient waiting for the nitrate levels to rise, so I put in way too many fish and fed them way too much. It worked great for about 4 weeks, then got really bad all of a sudden lol.

Thanks for your help guys. I'll check out Gammarus as well.