My 28 gallon bow front has been up and running for 5 months but in the last month or so I've had high nitrate readings (between 40-80). I did my weekly water change and vacuuming today and tested 3 hours later and I have at least 80 on the nitrates and suddenly I have a low nitrite reading .25. No matter what I do I can't get the nitrate down but it's higher than ever today.
The tank is lightly planted with about 8 plants.
5 head and tail light tetras
3 glo tetras
1 silver molly
2 female sword tails
I have two filters running a penguin bio wheel with a new filter in it for 2 weeks plus a cut to size nitrate filter pad for about 3 weeks. The other filter is an aquaclear 50 that has been running for about 4 weeks along side the biowheel. I took out the carbon and put a piece of cut to size nitrate filter pad.
I do between a 30-40% water change weekly and dig into the gravel when vacuuming.
I can't figure out why my nitrates are always so high and why I suddenly have nitrites today?
I also tested my 5.5 gallon betta tank and everything is fine with that although even that showed the nitrate a little high maybe at 40. Seems odd since I only have one betta who eats 3 pellets a day and his water is changed weekly also.
I checked the expiration date for my API test kit and it's good until 2017. I tested my water a few weeks ago and the nitrates are between 10-20 in the tap water. I'm at my wits end trying to lower the nitrates. I haven't cleaned any filter media in a few weeks, could that be the cause of the high nitrates? and since I haven't fed the fish today it can't be because of rotting food and there are no dead fish or plants. Last week I thoroughly cleaned everything meaning I removed the decorations and the silk plants so I could vacuum good, scrubbed the glass with my algae brush and put all new plants in.
Could someone please give me an idea of what to do to lower my nitrates?