I have 4 goldfish and a weatherloach in my fish tank.

Last week I cleaned the tank, it stunk and had a lot of algae and was due a clean anyway. I put the fish in a smaller bowl for a couple of days and the bowl didn't have a lid and it stunk the room out horrendously. After that I put the fish back in the original tank and the water was perfectly clear for about 2 days. I put in something to prevent algae which I'd never used before.

Now for the past couple of days the fish have been at the surface a lot to get oxygen and the water is cloudy and it's stinking the room out again although this time there is no algae (unless there's some kind of invisible algae that I don't know about).

Also If I'm not mistaken I can see a white blotch on each of the goldfishes noses which is flat and i know it shouldn't be there. All 4 of them.

I have a filter which to be honest I don't think works properly.