Backyard Aquaponics
A place to discuss aquaponics

My small indoor system is suddenly reading nitrites of the charts. Even after 2, 1/3 water changes the test tube turns bright purple in much less than the 5 minutes instructed in the kit. Ammonia and nitrates have dropped to near undetectable levels. I had to test twice to be sure. I guess this is why I haven't been getting good growth these past few weeks. The fish seem fine however. I thought that readings above 1ppm were dangerous for the fish but my fish are active, eating, and they definitely aren't gasping for oxygen.

I've stopped feeding the fish for now and I will do more water changes as soon as I gas off the chlorine.

If your Nitrites truly are "off the chart" and your fish are still healthy and feeding the I'd suggest you purchase another Nitrite test kit (make sure it's well in date and don't keep it anywhere warm) and see what reading you get.

In the meantime salt to 1 gram per litre of water just in case.

Seems odd, maybe clean the test tubes and try again.

I have had a weird reading in my system, only to find it ok when retested?

Well its not the test. I tested the tap water (zero), and my outdoor system (trace). I did another 1/3 water change still testing very high nitrites. I will continue daily water changes until it comes down. I might have some super fish or something. They still don't seem to be affected.

How do I test salinity? Is there an accurate way to do it with a quality DMM. I know that salt water has a lower resistance than fresh water. But I'm not sure if a DMM is sensitive enough to tell the difference with such small amounts of salt.

You measure salt content in water, you need a salinity refractometer or you can get digital ones too. Will be measured in ppt. Part per thousand.

What's your pH?


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Ivan Ph is about 8.0

After my 4th 1/3 water change the nitrites have come down to the 1.0-2.0 range. One more water change should do it.

How long do you think it takes to off gas .61 ppm of chlorine in a few gallons of water with a bubbler?

Im currently giving it about 10- 12 hours. I think I could get away with half that time but Id rather be safe than sorry.

I guess the pH reading is after a few water changes. It is quite possible that the pH could have drop low enough to cause problems with nitrification. Sometimes too much water changes will work against you as the bacteria needs time to build back up. I would think it would be better to stop there and add salt to 1ppm.


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Already nitrites have gone up to over 2.0. I think I'll move one of the fish outside tomorrow, there are only two. Even with all these water changes and high nitrites they seem fine but they are hungry. They are eating the waste that floats up when I siphon the water out.

Nitrites are still high but at least now I have high nitrates to. I think I discovered the source of the nitrites. I pulled out my old wheatgrass and discovered a bunch of rotten seeds that didn't germinate.

Nitrites have finally dropped. Just in time for the new fish food. No more flakes for these fish.