Hi, haven't posted for a while so here's some updated pix of my natural swimming pool/fish pond. I've had 3 golden perch and a koi and 10 or so goldfish in the swimming pool for the last 18 months and recently added another 32 golden perch to the bio filter pool totalling about 30 kg of fish. The 32 perch came from a nearby farm dam that I drained/transferred water as the dam was very low and the fish had to be rescued. The appropriate authority (can't remember who) said I couldn't let them go into the Murray river as they were farm fish and of unknown gene pool. Fair enough. So with nowhere else to put the fish in a hurry, I opted for the swimming pool's bio filter pool. I might add at this point that 28 snake necked tortoises came out of the dam and overnighted in the pool before being released next day in one of the Murray's billabongs. The perch were put into the bio filter about 5 weeks ago and seem to have had little impact on the system. The water always smells very clean when swimming. Yesterday I tested the system for ph, nitrates and ammonium using an Aquaspex stream survey kit. Ph is always about 7.6 with ammonia reading good as none and ammonium reading as good as none. I fed the fish quite a few yabbies when I first put the fish in but have not fed them much of late. What is a good fish food to purchase? I did want to get all the original fish out some time ago as ideally a very low nutrient level is desired in this sort of pool however I've only increased the potential nutrient load.... and they will need to be fed! The bio filter should have no problems catering for the fish but just how much fish poo do I want to swim in! Time to go fishing I think.