Zero Ammonia, High Nitrites and High Nitrates

[Steiner99]

My tank is a 20 gallon. I have had it for a month. I was hasty with the nitrogen cycling and I added Fritz Zyme 7 I read that it has helped people with their nitrogen cycle and allowed them to add fish immediately. Yeah that is too good to be true... I currently have 3 mollys, 3 guppies and 4 oto cats as there was a huge algae bloom (I assume now from the nitrite/nitrate spike). I noticed one of my male guppies fin turned cottony I believe fin rot. I tested the water and the nitrites & nitrates were very high so I did a 30% water change yesterday. Today I tested my waters and ammonia is 0, nitrites 0.50ppm and nitrates 20ppm. Idk how my fish are even still alive especially the oto cats. I added some aquarium salt for now. Should I go buy Prime Seachem? Should I change the water till there is no nitrites? Should I go & buy a cycled filter? Any advice is much appreciated.

[ColdKoi]

Water changes are your fiend with an uncycled tank. Do a 50% water change, wait an hour or 2 and retest the water. If you still show closer to .5ppm nitrite do another 50% change. Your nitrates are well within acceptable levels, which shows some cycle has started at least. Just keep up on water changes to keep ammonia and nitrite levels low

Cycled filter media would be great. But if you have to pay any real amount for it, it’s probably not economically feasible at this time if you’re close to achieving cycle anyways

[Aiken Drum]

Your water parameters are right where you want them to be during a fish in cycle. If your nitrite gets worse than that, or if you see any ammonia alongside your 0.5ppm nitrite then do a water change to bring it down. 0.5ppm combined ammonia and nitrite is your upper target. This is a relatively safe level, while leaving enough waste in the tank to cycle it.

Nitrate can get much higher. 40ppm is generally considered a good upper level, but many people keep healthy fish at much higher levels of nitrate than that.