Help!! My nitrates are at 20 today. 1/3 water change last week at they were at 0. Tank size is 125g. I added 2 clowns a week ago. Any ideas? What should I do?
Yes a starfish dying could cause it. Anything that would releace nitrogen compounds. Decaying organic material is generally the cause, and if I recall it can cause your phosphates to climb as well.
AmQuel will "lock" ammonia I believe. Do a large water change and run carbon .... check the nitrates again and if they're still high repeat the procedure.