Hello, I used to be a member of Bidka years ago when I last kept Discus and I have now got back into the hobby and I suppose back to having problems again. I have 5 Stendker discus, I had 7, they are about 20cm across I've had them about 2 years. They are in a 450litre aquarium that is planted. The water gets a 50% water change once or twice a week depending on how much time I have, it is filtered from tap through a Chloramine, Activated Carbon and Sediment filters which are replaced yearly. It has a fluidized bed filter for a biological filter and an external mechanical filter thats about 20 litres in size. It has a Co2 fire-extinguisher injection system. They are fed a mixture of beefheart with various other things like mysis, bloodworm etc. We have had a very difficult six months and the fish have gone through a lot some of it my fault and other things we couldn't foresee. We had a inflow tap break and so flood the tank (and our living room) overnight which meant the three inline heaters we had were unable able to cope and the fish all got very cold and it was touch and go for a while but they all survived. We have forgotten to turn the fluidized bed filter back on after a tank change at least twice ( we have a baby thats coming up for 6 months old and a difficult 4 year old and we are generally operating with very little sleep). And then just as I thought we were coping better and we had put various solenoids in place to prevent the other problems we were having we had another incident. I did my usual Saturday morning water change about three weeks ago afterwhich the fish started behaving weirdly. Something was wrong, the Turquoise's stress bars were up and stayed up, then the Dark Angel kept darting but all the other fish seemed fine. The they all started behaving jumpy (this is all over a couple of days) I started to move them all into a hospital tank because they were getting worse but they were jumping full out of the water in that tank so I put them back in the main tank and did 50% water changes everyday for two weeks, and they recovered, it seemed. By this point I thought it was a miracle they all survived anyway, until now.A local fish shop owner said he had had a lot of fish owners coming in saying their Ph was going haywire and there is a suspicion the local water board had dumped a load of acid in the system, we are in Cambridge and our water is very hard and cambridge water are doing 'emergency work' in the road near by. Anyway I have now lost two fish, the last one died about an hour ago. 4 days ago it was immaculate and then in the morning it had a puncture in its flank that was perfectly white but you could see it went through the scale layer. I moved it to a hospital tank and started dosing with salt and then Melafix. It got staggeringly worse in four days and had bits of white tissue coming off and bits a red flesh in it too and increased tenfold in size, it was originally less than a cm2. The photo I have uploaded is of this dead fish, in the photo it looks like the whole wound is red but this only happened once it died it was white before. I couldn't tell if it had damaged itself on a rock initially, but I lost a Marlboro red about a month before in a similar way except it was his eye this happened too, I thought at the time it might have been a one off but now this has happened again I'm worried its going to happen to all of them, I don't think it can be a coincidence. They all look so healthy and are feeding well etc. Both the ones that died looked immaculate until they become grossly disfigured overnight. I've looked up every condition I can find and I can't find anything it sounds or looks like, I've never seen anything like it before. Ulcers are the closest thing I've seen to it but to be honest they are red with white trims and neither of my fish looked like that. Obviously all these fish have been put through hell and I presume are immunocompromised and I need to keep them all stable. The parameters have all seemed better than expected without large leaps in Ammonia that I would expect but of course they are vulnerable and I don't know what to do. If this is some sort of bacteria eating the fish should I put loads of some Antibacterial into the main tank and would that then further compromise the bacterial filters? And living in England I don't even know what antibac's are available. We have tried to find a vet that is prepared to deal with fish but haven't been able to get one thus far.