My 28 gallon has been established for about 6 months but I've been having some problems with Nitrates. I have a bio wheel filter that has practically stopped and I've tried everything to get it moving again but I give up. Five days ago I bought and set up an Aquaclear 50 Filter and have it running WITH the bio wheel.
Today was my weekly maintenance day and I changed about 40% of the water, scrapped off some algae, vacuumed and moved some decorations around. I decided to check the water parameters just to see if the nitrate has gone down and I have an ammonia spike!!! what the heck!! how and why did that happen? Nitrites are 0, Nitrates still high between 40-80, ph is good 7.2, but the ammonia is at .50, that hasn't happened since it was cycling. I've never had ammonia since it's been established.
I looked at my plants today and vacuumed it as good as I could to try to get the nitrates down so I don't know what is going on. I haven't fed the fish today so it can't be that. I'm not over stocked I have:
5 head and tail light tetras
3 Glo tetras
1 dalmation molly
2 unknown ( was told they are sword tails but I don't think so)
Can anyone give me an idea of why my ammonia spiked and what can I do? and any thoughts on why my Nitrates never go below 40?