Bloated Fantail

[RoseTeal]

Hi

We have a 70 litre freshwater tank with 5 fantails in it. We started the tank about 18 months ago - we have two filters and an aeration pump in it. Just recently one of the fish has become very bloated - his scales look a little dull and he doesn't hold his tail up as much as the others. He passed some waste about a week ago that looked clear instead of the usual dark colour and we haven't noticed anything since. He tends to stay in one area of the tank and doesn't swim about very much. However his appetite seems unchanged and he perks up and swims around appearing to feed with the others. We had some small gravel in the tank which we have now removed as my husband is convinced that he had swallowed some of the gravel and has a blockage. Has anyone else ever experienced this? Any suggestions?

Cheers

Rose