Ok, this is my second tank (the first one I did a fish-in cycle due to being a total noob, it took about a month, there were no casualties etc, all happy). So, after my initial success I decided to start up a second tank to house a betta and some corydoras. I started with 6 corydoras in the tank (it's a 10 gallon, plant substrate with lots of live plants, driftwood etc.) and an internal filter. I wish I'd been more patient and not been such a noob with doing this tank as well. I realise I should've waited to put any fish in there, and trust me next time I will do a FISHLESS cycle for sure, I have learned my lesson here guys. It has been 2-3 months since I set this tank up, and the ammonia readings always creep back up to 4ppm+ if I don't do regular water changes every other day or so (I do water changes with API Stress Coat+ around 20-40% depending on how high the ammonia is, to keep it around 1-2ppm if possible). I've tried adding all sorts of products, tried not adding products, tried not doing water changes, tried doing more water changes, tried adding ammonia remover, the lot, and STILL this bloomin tank will not cycle. I even swapped the filters with my other tank (which stayed cycled), but even that hasn't worked. I'm seriously losing the will to live with it... The corys seem to be doing ok, but I might move them into my other tank just to let them have some decent water quality while that tank cycles (it would be temporary, there's nothing in there that they can't be with and it's currently under-stocked anyway). I'm using an API Master Test kit: Ammonia: 4 Nitrite: 0 Nitrate: 0 PH (not tested - I'll do this later but it's usually around 7-8) Any ideas?