Am in the process of organising a sensory room for my ASD son and as he adores my granda's aquarium I decided to get him a small one to start off with. The pet shop assured me the 15litre aquarium was fine and we could have three goldfish in it. So naively we bought the aquarium, set it up and three days later added our three goldfish. Needless to say the goldfish are now in that great pond in the sky and I'm not a happy bunny. I have the tank still running to cycle ( didn't know anything about that) and bought a freshwater testing kit. Nitrite and nitrate levels are now zero, ammonia is still .5 pmm and the filter is running. Have water conditioners, ammonia remover and stress enzyme added. Before I buy another fish what can I do to aid the cycling process and what fish should I get? We are going to get a bigger aquarium (Santa/birthday pressie) but the fish really help keep him calm and would love to have some for him to watch in the meantime. Thanks for any help. and trust me lesson was learned.