This is a discussion on Is this right...or very bad? within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; -->
I currently have my 36 gallon aquarium cycling with 5 bloodfin tetras. It's been cycling for about 3 weeks now and I have been ...
I currently have my 36 gallon aquarium cycling with 5 bloodfin tetras. It's been cycling for about 3 weeks now and I have been testing the water bi weekly. My nitrites are the highest the test strips will indicate but as I understand this is part of the cycling process to get those good bacteria going. My concern is, and here is where your opinions come in, I have white sand (substratea) by marineland...blah blah blah. Lately through the cycling process I have noticed the sand to begin getting covered in little brown spots which appear to be bacteria. I have been really concious not to overfeed my fish. I also believe that during the cycling process you should NOT do any water changes. Is this discoloration normal and ok on my sand?
I believe the brown on the sand in algae. Algae growth is normal in a cycling tank.
As for your fish, its amazing that they are still alive living in those nitrites. Did the ammonia already drop to zero?
I have heard some people say to not do water changes doing a fish cycle, but I do not agree with it. Both ammonia and nitrites are toxic to your fish. Anytime I have cycled with fish, I tried to keep both ammonia and nitrites under .25 ppm through water changes. Sometimes daily 25-50% daily water changes where needed. I did not loose any fish this way, and I still had good cycle times, 6 weeks or less.
I agree with Twistersmom on all points. The brown in the sand you are seeing are diatoms (type of algae) which is common during the cycling of a new tank. Once cycled and a few water changes it'll die off. IMHO, if the readings you're seeing are accurate you need to do a water change NOW. It will not disrupt your cycle.
I agree with the above posts. Water changes during fish-in cycling are a MUST. I would much rather keep the fish healthy and comfortable during cycling with water changes than subject them to ammonia and nitrite poisoning.