I'm perplexed at the moment.... Slagter might need temporary tank space for his Wild X's while their tank is being repaired/replaced. So yesterday I whipped out all the test kits to double check params pH 7.0 Ammonia 0ppm Nitrite 0ppm Nitrate (API test) 0ppm Nitrate (Sera test) 10ppm P04 (Hagen/Nutrafin test) > 5 ppm Now the tank has been in a fishless cycle for close to a month. I only have some algae covered driftwood and bio-rock in the tank in addition to filter media(Ceramic rings, filter floss, Sera Pro Peat and 2 air driven sponges). Any ideas? Possibly from algal death? I also test my tap water to make 100% sure, result was 0ppm for P04. Time for a new test kit maybe?