Angelfish sinking like a stone

The eheim filter probably has a thin black pad, which is carbon impregnated, so remove that, and yes I'd carry on with a 4th dose of octozin.

No thin black pad in this one, just a thin blue pad at the top and a thicker white pad that sits on top of the biological media. I have looked online and seen what you mean but I think I would have to buy and add that in separately. Added the 4th dose today.

Akasha, I really hope your angel recovers, I have read online that some people recommend a 3 x dosage but I clearly have no experience or authority to know if this is actually a good idea! You have at least acted far sooner than I did with Feng so hopefully you got there in time.

Shui seems to be totally fine visually but doesn't seem to be eating much. The problem is the 6 platys I have are eating machines. Everything I put in, they rush to and eat. Trying not to overfeed them, but putting in enough for there to be something left for Shui seems to be a tricky balance right now! Maybe Shui is just a bit sad at the moment from the loss of Feng!

Thanks Pete .. he's hanging in there ... he doesn't appear to be sick in any way other than having an all over swelling for which I have no explaination for.

In terms of feeding you could try feeding tiny amounts in different areas on the tank. I tend to do this with frozen food. I use a turkey baster to suck up a small amount and then squirt a bit in different areas around the tank. This is so they all get a chance to have something otherwise my harlequins and tetras would gobble the lot