TCLynx what did you find?

[urbanfarmer]

Please post whatever you are so excited about!!! I WANT TO KNOW!

[TCLynx]

Ok so before you posted any links, I did a quick search which came up with this document.

http://www.hos.ufl.edu/vegetarian/Water%20pH%20Impacts%20Sustainability%20of%20Recir culating%20Aquaponic%20Systems.htm

Which seems to state (in a quick skim reading) that they think aquaponics will do better with a pH of 8. Now I know that a the ammonia to nitrite conversion in a bio filter will function better up around that pH but simply taking ammonia levels and equating that to better complete function of aquaponics doesn't quite sway me. There are so many other factors to take into account.

[TCLynx]

An back to the Constant Flow thing? So you seemed to be saying that for a low fish load system to work well, the system would have to be near constant flow. Well the only support I've so far found is the following quot from the link you shared from the University

Constant-flow systems have a distinct advantage in aquaponics, where micronutrient concentration is reduced by a high pH (Tyson 2007, Tyson et al. 2008). In soil or reciprocating hydroponic systems, the water and nutrients nearest the roots are quickly taken up by the plant. Movement of more water and nutrients into the zone immediately around the root is slowed by the soil or media, leading to a zone or "halo" of nutrient depletion around the root. This effect means a higher overall nutrient concentration is needed to avoid unacceptably low nutrient levels immediately around the roots.

If the solution is constantly in motion, however, depleted zones do not usually occur, and more dilute solutions will fulfill the plants' requirements. Therefore, nutrients with low solubility at high pH (such as Fe and Mn) may have fewer deficiency problems in constant-circulation systems than in reciprocating systems. However, growers should carefully monitor for low nutrient levels.
The supporting documentation doesn't really support the statement you made. It kinda says, if you have to keep the pH high to help the bio-filter support the higher fish load, then you would do better to use constant flow to help the plant roots have better access to the likely locked up trace elements.

Well if you are going to have a really minimal fish load, you won't need to keep the pH that high in order to allow an undersized bio-filter to keep up and therefore you won't need to utilize constant flow or even foliar feeding to get good plant growth. And I think the pictures in this thread may help support this backyardaquaponics.com/forum/viewtopic.php?f=1&t=8621. It is an experiment where they are running three systems side by side, one with autosiphon, one with constant flood, and one that is timed flood and drain. So far the plants in timed flood and drain seem to be doing best while constant flood has been in the middle and the siphon system is still lagging though the constant flood has been doing better with bio-filtration.

Anyway, I've been finding that different things do better in different situations.

Granted, the extension service is geared to helping commercial agriculture not the home aquaponic hobby. Taking a statement out of context from one of the publications and trying to apply it to another situation is kinda like taking Nelson and Paids mention that they have found 74 degree water to be the best compromise between Tilapia's best growing temp and the best growing temp for lettuce in their controlled environment growing conditions and then using that to tell people that the water for aquaponics Must be 74 degrees. The truth is it all depends on the goals and situation. We know aquaponics can work great with a far wider range of temperatures.

[urbanfarmer]

Hm, apologies... badflash pointed out what I linked was an 8 page document... what I have is 120 page dissertation that was successfully defended. Let me find that and the section that led me to that previous statement... I have a long day tomorrow, but hopefully I can reply then if not the day after for sure.

[urbanfarmer]

http://etd.fcla.edu/UF/UFE0019861/tyson_r.pdf

Here it is. I have been mulling over this paper for the past few days, but I believe what I referenced is around page 59. I'm tired; so, I will have to relocate the passages, but I think it was Dr. Tyson's own conclusion I was regurgitating. It said something along the lines that if the nutrients are very low in the water, a constant flow will allow the plants to still uptake enough nutrients without loss of yields. Also, I was not trying to say a CF system is better. A flood and drain system that is constantly flooding and draining would yield the same effect, NFT, or anything like that. Anyway, happy reading and let me know what you think! :mrgreen:

[rfeiller]

talipia are naturaly from waters with a high ph.

[TCLynx]

talipia are naturaly from waters with a high ph.

Yes, does that mean that all aquaponics systems must run with a pH between 7.5 and 9? I don't grow tilapia anymore cause I'm unwilling to spend money to heat water and we like other fish better anyway.

The experiments in the above linked paper I was looking through were with cucumbers in trickle through perlite bio-filters.

So far in my reading, they didn't actually trial any flood and drain. They were mainly working at establishing the best pH for bio-filtration in said trickle through perlite bio-filters and then they also did a trial cycling up the bio-filters where they also added hydroponic nutrients to the water to see if that inhibited the bio-filter and how the different pH affected things.

[urbanfarmer]

That is just PART of the experiment. He did multiple stages of experimentation because he wanted to test ALL the array of nutrients to bang it out with one paper. He is trying to reconcile the pH for an AQUAPONIC system between known pH levels for both hydroponic and aquaculture. Given the best pH for each respective and then testing pH for perlite biofiltration. He goes from there to expand on these known values to get a better idea for aquaponics! This guy in on our side, I promise!!!! :mrgreen:

And yes, I know it takes a while to get through. I have only had time to get through 70 pages of it... although I skimmed the last 15 or so pages because I couldn't wait... LOL

[badflash]

Tilapia thrive in a wide range of pH and hardness values. You should taylor the conditions to what the plants need. The biggest issue is temperature. Tilapia are optimized at 85F, few plants like that.

The system I envision has two separate loops, one for plants, one for fish. A small blowdown from the fish, enough to keep the nitrates in check as well as the solids, go to the plant loop. Purified water would go from the plants back to the fish. Only a small flow, just enough to handle nitrates would go back & forth. This requires a separate bio-filter for the fish.

This would allow for different water temps and conserve heat or cool.

[TCLynx]

Tilapia thrive in a wide range of pH and hardness values. You should taylor the conditions to what the plants need. The biggest issue is temperature. Tilapia are optimized at 85F, few plants like that.

The system I envision has two separate loops, one for plants, one for fish. A small blowdown from the fish, enough to keep the nitrates in check as well as the solids, go to the plant loop. Purified water would go from the plants back to the fish. Only a small flow, just enough to handle nitrates would go back & forth. This requires a separate bio-filter for the fish.

This would allow for different water temps and conserve heat or cool.

I suppose this could be done if it's what you want. I'm unwilling to heat or cool the water going either way so I'm going with fish that can do with the natural temperatures and I grow plants accordingly depending on the time of year.

My aim is to get a system nicely balanced that doesn't require a lot of extra attention from me. I'm going for backyard scale, balanced, stable, aquaponics systems for feeding the family. I'm not trying to optimize for commercial production of anything.

I like running with a pH that is fairly stable (doesn't require daily pH testing) and fish/feed loads that don't cause the ammonia or nitrite levels to get over a trace even if the pH is running as low as 6.5. I like the pH between 6.5 and 7 since that usually avoids me having issues with nutrient lock out. I have run systems that run a constant pH of 7.6 and even with constant flow, nutrient lock out of some things still happens and I don't really like having to add chelates all the time.

[badflash]

The idea would be for the fish to be at 85F and use evaporative cooling to cool the water for the plants. A simple spray bar would do for that. I find that properly cared for the pH goes to around 7, which is just what I want. I keep some aragonite gravel in the tank for a buffer.

[TCLynx]

The idea would be for the fish to be at 85F and use evaporative cooling to cool the water for the plants. A simple spray bar would do for that. I find that properly cared for the pH goes to around 7, which is just what I want. I keep some aragonite gravel in the tank for a buffer.

That may work in some environments though the cost to heat the water as well as loss to evaporation might be unappealing to some people.

I don't think a spray bar will chill my water much when it is naturally warm enough to heat the water to that temperature. I am in Florida where evaporation cooling is kinda a joke (Swamp coolers don't really work in a swamp.)

[badflash]

NY and Florida are pretty different. Spraybars are used routinely to cool pools in the summer. Dry climates use this too. The water is easy to keep at 85F from June to September, the trick is to cool it. Winter may be a different issue. No single solution will work for everyone.

[TCLynx]

No single solution will work for everyone.

Yep that is the whole truth.