Aquaponic Gardening

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Hello all.  Here's what happening:

System: CHOP: 230 gallon fish tank, 200 gallon grow bed with expanded clay, 150 gallon sump.  Pump runs constantly and cycles grow bed about four time per hour (bell siphon).  

I cycled the system before adding fish or plants but added more clay after cycling.

After adding fish and young plants, I saw "typical" spikes in NH3, NO2 as the bacterial colony had to grow to handle the new NH3 levels.  NO3 levels seemed to be rising normally.  

Now after 2 weeks I'm seeing good NO2 -> NO3 conversion (NO3 levels are climbing daily) but the NO2 still remains high.  NH3 is almost non-detectable.  So, I have lots of good bacteria converting NH3 -> NO2 and some NO2 -> NO3, but the second colony just won't seem to grow enough to handle all the NO2.  I tried re-seeding from an established system a week ago but that hasn't seemed to help yet.  

I've been doing daily 40% water changes so the fish don't get stressed (de-chorainated, de-chloramined, pH adjusted water).  But daily levels before water change are pretty constant:

0 - 0.25 ppm NH3

5+ NO2

30+ NO3

During this time the pH has dropped slightly from 7.2 to 6.9 (I always adjust new water to the existing water).  The plants (and some algae in sump) are growing like crazy but I just can't get the nitrites to crash and I'm concerned about long term effects on the fish (tilapia). Temp is 86F.

Any ideas? Am I just being impatient? Am I just being a nervous fish daddy?

Thanks,

Bill

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Did nitrites go to zero, or did you consider it done when you started to see nitrates?

you're early yet - keep at it - good thing tilapiare tough

I think I see your point.  During cycling, nitrates never went to 0 but were below 0.5 ppm and nitrates were 40+

Jeffrey Ihara said:

Did nitrites go to zero, or did you consider it done when you started to see nitrates?

RIght, they are hardy fish. I'm aerating like crazy and am glad the pH is good.  Fortunately there's no sign of brown gill or lethargy.  They're voracious and I wish I could feed them more! 

George said:

you're early yet - keep at it - good thing tilapiare tough

Fish and bacteria might be happier at 8.0 or so.  Salt helps fish cope with nitrite.  I won't try to expound from memory but searching would probably turn up some useful info on those topics.

Your system is very attractive.  I need to rebuild mine along those lines - my wife would love it.

Good suggestions.  I'm actually adding a little bit of "safe" salts as I adjust the pH.  I didn't want to pH to climb too much because it's really sunny and warm here in Key West and the combined high water temp and high pH would lead to increased ammonia toxicity.  I'm considering getting a chiller to keep the tilapia just a bit happier (especially in August) and to keep the plant roots cool to help keep them from bolting.  That''ll have to run on AC power but I'm planning to convert the pump to solar supplied DC soon so the system will be as much "off the grid" as possible.  

Thanks for the compliment.  My wife was a bit concerned during construction but now says it looks like lawn furniture!  I was worried about our very conservative HOA so I wanted it to look a nice as possible (e.g. no plastic or "clutter").  I ran as much of the plumbing along the fence as possible and I'll probably paint the exposed PVC over the tanks to match the wood stain.  Overall on the wood white paint would have reflected the heat better but the "natural" stain does look a lot nicer!

George said:

Fish and bacteria might be happier at 8.0 or so.  Salt helps fish cope with nitrite.  I won't try to expound from memory but searching would probably turn up some useful info on those topics.

Your system is very attractive.  I need to rebuild mine along those lines - my wife would love it.

You may get a good flush of rainwater soon.

Wouldn't just some shade over the tank be good enough for tilapia?  I thought they were ok with very warm water.  Someone else may be able to speak to it - There are plenty of tilapia in the southern latitudes.  I'm at 30N and my water is at least as warm as yours.  Bluegill don't seem to mind.

True, tilapia are fine in warm water (they can tolerate a wide range of about 55-95F), but they grow faster (and produce more waste in the process to "feed" the plants) in the middle of their natural temp range (low to mid 80s).  Even with the tank in the shade, temps would climb into the high 80s and even 90s.  Add to that the heat absorbed and transferred by the clay in the grow bed (especially since we want to avoid evaporation to reduce the need to add water) and it can get very warm - approaching the high end of their range.  I specifically selected heat tolerant plant varieties, but they'll still be happier with slightly cooler water.  

Yes, we got some great rain last night but it's a toss-up right now whether or not we get anything significant from Chantal.

I'm familiar with your climate; we moved here from Kingsland, GA.  It probably get's hotter AND colder where you are than it does here (unless you're within a few miles of the coast) so I'm lucky not to have that challenge.  

George said:

You may get a good flush of rainwater soon.

Wouldn't just some shade over the tank be good enough for tilapia?  I thought they were ok with very warm water.  Someone else may be able to speak to it - There are plenty of tilapia in the southern latitudes.  I'm at 30N and my water is at least as warm as yours.  Bluegill don't seem to mind.

I have great news!

It appears that I posted my question just one day too soon.  The day after I posted my question about high nitrites, the concentration was a bit lower (2-3 ppm).  I opted not to do a water change to see what would happen if I just left the rest of the nitrites for the bacteria to "feed on."  Sure enough, the next day and since then the levels of both ammonia and nitrites have been undetectable (or nearly so).  

The really great thing is that the nitrate levels have also been dropping even though I've been increasingly feeding the fish.  Today the nitrate level was only 10 ppm.  Plant growth has really taken off so now that the bacterial colonies are well established I can feed the fish to their hearts' content and the plants will be loving it too.  

Next step: worms to start converting solid wastes that are being increasingly produced by they fish.

and down in the land of year round outdoor gardening too.  

Let me know how the DC pump works out for you.  I'm still searching for durable low wattage DC - using Shurflo bait pump right now.  Converse is good if you need composting worms.

Oh, please let me know if you find anything :D I've been having a  hard time with that too.

George said:

and down in the land of year round outdoor gardening too.  

Let me know how the DC pump works out for you.  I'm still searching for durable low wattage DC - using Shurflo bait pump right now.  Converse is good if you need composting worms.

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