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I am having a water chemistry problem. I have a single IBC flood and drain set up with a single grow bed growing leafy greens (basil, sage, arugula, swiss chard, and lettuce). The 175 gallon system finished cycling four weeks ago. Three weeks ago we added three shubunkin goldfish and two channel cats. Two weeks ago we added five more shubunkins and four more channel cats. The fish are all 2-3 inches long. Everything seemed to be going okay with happy fish and readings at zero across the board.

Last night I tested the water immediately after feeding the fish and had 0.25 ppm ammonia, 0.5 ppm nitrites, and 2.5 ppm nitrates. I salted the system to 1 ppt and retested this morning getting the same numbers across the board. I have not fed the fish today and this evening I tested the water again with the same results. I changed out 10% of the water volume using filtered tap water and tested again 30 minutes later with the same results. The pH has remained steady at 6.4 since the spike started which is odd for this system which usually drops quickly by 0.2-0.4 pH units each day and I am adjusting the pH daily to keep it at 6.4-6.8 (I ordered some shell grit, but it hasn’t arrived yet).

Are my fish in danger? The goldfish are happy, playing, and begging for food. The catfish are hiding in the back of the tank (like always) where I can’t see them and they refuse to come out unless there is food. I don’t see any dead fish. What should I do, if anything? The only change this week was a change from flake food to AquaNourish for fingerlings (the new food is really tiny and sinks so it is hard to judge if I am overfeeding them...I have never measured how much I am feeding them, but they like the new food more and are eating a lot more of it in the five minute feeding periods). I had been feeding them as much as they would eat in five minutes two to three times a day until I stopped feeding them yesterday evening.

I was planning to add a few more goldfish and channel cats to the tank soon, but I am not sure if I should anymore in case I am overwhelming the biofilter already. Thanks in advance for any advice!

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I don't think that's very much of a nitrite spike. Your pH -- how you need to keep it up -- is unusual in my (limited) experience.

I've had much more severe nitrite spikes and I've lost maybe 5% of my fish over 3 months. It's good to be concerned though ... stay vigilant.

Okay, thanks. I guess I must be overly worried being new to AP. For future reference, how much of a nitrite spike is enough to be worried? The numbers were the same again this long does typically it take for them to come down if you aren't feeding the fish? Should I worry about adding more fish and overwhelming the biofilter?

The water pH deal is a bit odd I think. The water comes from the local man-made lake and comes out of the tap at pH 8.2. We always thought it was hard water because it leaves water spots everywhere, but within three days of starting cycling the pH started dropping. After one week it had dropped to 6.0 (or less) and I have been trying to keep it above 6.4 daily ever since. Apparently it has zero buffering capacity. I ordered some shell grit which will hopefully help keep me from having to check pH up to twice daily (once it finally arrives). The aquarium guy (two towns over) doesn't have this problem (different water source) and suggested I keep discus fish! Maybe I'll make a new system indoors and make aquarium owners jealous! And grow some blueberries too!

The water changes are possibly keeping the PH from going down, which is good.  You might want to search KH, calcium hardness.  Do you have plenty of filtering?  

Good move stopping the food - You'd best not feed until nitrite is zero.  

Probably, your biofilter is still ramping up.

Yeah, those waste levels are pretty low. Keep an eye on the water as always and don't stress about it.

I actually have no filtration apart from the bacteria and plants. I have never had the water tested for KH or calcium hardness. I will run a sample by the local pool supply store and see if they will test it for me (or if they have a test kit) and will let you know what I find.

So, where is your bacteria?  Do you have gravel beds?

So I sprung for a Taylor Test Kit at the pool store and here is what I discovered....

Tap water: pH 8.0; Total Alkalinity 110 ppm; Calcium Hardness 50 ppm

Tank: pH 7.2; Total Alkalinity 10 ppm (only one drop to turn from green to red); Calcium Hardness 250 ppm

Those numbers seem odd. Shouldn't the tap and tank reflect each other to a certain extent instead of being opposite? They don't test KH.

Interestingly there was a pretty big discrepancy between the Taylor kit pH which was 7.2 and the API kit pH for the tank which was 6.4. Is the API test kit inaccurate?

I have hydroton in the grow bed. I am attaching some pics of the setup. The lettuce and arugula bolted and look a little scraggly/dead because we had a serious heat wave last week. The tank got up to 85 F last week.

I still haven't fed the fish (almost 48 hours now) and the nitrites are still at 0.5 ppm and ammonia at 0.25 ppm.



I have found that checking your water be you feed the fish in the morning and wait until the next morning to check the water again. If I find ammonia or nitrite I feed less, until I have 0ppm ammonia and nitrites. This helps me find the right balance of waste my bacteria can handle in 24 hours. The fish can go weeks without food, so don't let them fool you. Your water chemistry is more important for them and your plants.

That sounds like a good idea, Kent. I'll give it a try when I start feeding them again.

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