Poorly goldfish

Question

Fish   Hi I bought a goldfish four days ago and he seemed ok for a day but then he began sitting on the bottom of the rank and not moving. Today I noticed his scales seem to be coming off his tail looks like they have nearly all come off and looks like skeletal. I have a 30l tank with a filter which I had set up for a week before buying him. The shop told me to only buy one then add another fish a week later.

Answer
Nicola,
Your tank has not cycled yet. It take 6 weeks and sometimes longer. You have very bad bacteria in the tank, which is normal, but there should not be any fish in your tank. Are you using a good water conditioner? You have to test your water daily, with a liquid water tester. You will be testing mainly for ammonia and nitrites. If the level of either one is zero, you have to do a water change. We do this by removing 25-30% of the water and replacing it with clean conditioned water. If you do not do this, your fish will not survive long.