Hi,

I have a female discus who stopped eating two days ago. She has turned a bit dark in colour, is bloated and hangs at the top of the tank. Please see attached pictures Click image for larger version. 

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I have a 4 by 2 by 2 tank with a sump at the bottom (total liters approx 530). I have four large adult discus and two peppermint catfish. There is no substrate to make it easier to clean. We have heaps of the expensive stone in the sump that promotes beneficial bacteria colonies.

The water conditions appear to be pretty stable:

pH - 6.4 (the water tends to want go acidic for some reason. Tap water is pretty alkaline and use pH down to adjust it to neutral)
Ammonia - 0 to 0.257
Nitrates - 0
Nitrite - 0
Temp - 32 c

This problem seemed to occur after I fed them live mosquito larvae from a pond that we had just installed in the garden. The pond was teeming with life (very quickly), snails, worms (?), tadpoles, mosquito larvae and I may have introduced something nasty which has only affected her.

Around a week ago I noticed a white stringy poo and so treated them for fluke and tapeworms (I don't treat for worms unless I have to). They flare their gills a bit like it is difficult for them to breath so I thought it might either be lack of oxygen (plenty oxygen now) - this started maybe two ago. One other discus predominantly breaths from one gill. Then I noticed that she and the other with breathing problem, rubbing themselves on stuff a couple of times two days ago. So yesterday I treated them with Kusuri (fish wormer, fluke and parasite killer) yesterday. I have had the medication for a couple of years now and notice on the packaging that it should be used within three months of opening. The best before date is 05/15. Could the medication be ineffective? My main concern is the female who has stopped eating two days ago (she usually has a very good appetite) and appears to be moderately constipated. The two treatments for fluke worms etc doesn't seem to have helped with the breathing at all. I also did a 25% water change after using the the first lot of medication as per the instructions. I am thinking about treating with epsom salts for the constipation? Not sure if I should be treating with epsom salts while the Kusuri treatment is in the tank??

Going to set up a hospital tank now.

Any help would be VERY much appreciated!!