NEED HELP! High nitrite and low nitrate

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Feb 29, 2024
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I have a 55 gallon as well as a 150 gallon aquarium in my room. The 55 gallon i have had for about a month now (borrowed filter media from a friend to get tank fully cycled before adding fish). I have a sun sun canister filter on it as well as my 150g. The 150g i just set up about a week ago.

The 55 gallon was fully cycled with no issues handling bio load before i took two out of four trays in the canister and swapped them with the new trays in my canister for the 150g. My goal was to quickly cycle the 150g but my plan failed.

Issue #1: The 55g now has been struggling with high nitrites for about a week now. I have been doing daily 70% water changes, have been adding api quick start as well as having nitra-zorb in the canister. Its been over a week now and i can't lower nitrite levels.

Issue #2: My 150g still has no signs of nitrate, have had heater on, have added quick start, as mentioned early i added cycled media. Still no signs of life.


Also looking for advice on how to solve high nitrite in 55g
Sorry, but are there any fish in either tank? Because the advice will be different, depending on whether there are fish or any other creatures living in the tanks.
A fully cycled tank should have zero ammonia and zero nitrites and some nitrates. If you have fish in the tank while it is cycling you should do more frequenct water changes to keep the levels at bay so the fish don't suffer. A good cycle is indicated by having an ammonia source that is cycled into nitrates as fast as possible. I know the cycle is done when I have zero nitrites after adding an ammonia source, meaning the ammonia is converted to nitrates faster then it can be seen by the nitrite test.

If you have fish in the tank please follow the fish-in cycle steps listed here --> Cycle Your Tank! A Complete Guide For Beginners

The nitra-zorb is probably good for starting the tank, espically if you have fish in there. It might lengthen the time for the tank to be fully cycled though. I've not had much success with it reducing nitrates once a cycle has been established and live stock added to the tank.

I'm not certain on the question about adding water from the 150 gallon tank to the 55 gallon to kick-start the cycle. I think you need to make sure there is an ammonia source first, then the biofilter will build up and then convert the ammonia to nitrites then finally to nitrates.

When I cycle a new tank I don't just take estalblished media from an existing one. I usually add a rock from the established tank I also add an ammonia source and test to make sure the cycle is there and well established first, which usually takes about a week or so from when I've done it in the past. I use Fritz Pro Aquatics Pure Ammonium Chloride as the source. This doesn't mean you should use this as an ammonia source. For fish-in cycling the fish and the food you feed them are the ammonia source. Never add additional ammonia if you already have live stock.
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Hello evan. Provided you have just a few, small fish in such a huge volume of treated tap water, you should have a very small trace of nitrogen in the water, if any. Certainly not enough to harm the fish. This is because the small amount of waste material produced by a few small fish will be diluted in such a large volume of water. I doubt such a very small trace of nitrogen would even show up on a water test. Another thing. If you're dosing the bacteria starter according to the instructions, you shouldn't have such a level of nitrogen in the water.

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