Cold Water Tank.. Help Please

[Arktica]

HI there, i've had a cold water tank for a couple of years with assorted goldfish and a couple of pleco's, i recently added 4 weather loaches and my other half has placed sand in the tank for them to bury in. i noticed that one loach had a fungus on its mouth so i did my weekly water change and added interpet anti fungus treatment. since then (last friday) we have lost
1 pleco (no visable symptom)
1 gold fish (fungus over mouth/head)
2 weather loaches (redness on under side)
1 poor mans tetra (no viable symtoms)

My main issue is since that water change the tank has become so cloudy that you can't even see the fish. the cloudiness seems to be this clear slime which is taking over the tank and clogging the filter which requires almost daily cleaning now to provide enough oxygen. im concerned that this is also clogging the fishes gills as they mainly hang around the top [of the tank] in a very close group breathing from the air there.

today i did a 50% water change which appears to have had no visable effect on the fish or the slime.

any ideas please as? im stumped and dont want to loose the rest of the tank


edit:

Size of aquarium: 120 litres
Types of fish : goldfish x5 small plecos x3 weather laoch x 2 poor mans tetra x 5
Filtration used and how do you clean it and how often - flueval 3 cleaned weekly
How much in the way of water changes and how often -- 25% weekly ( plus 50% today)
Do you dechlorinate - tetra aquasafe
How long has the fish been sick and which medications are your currently using or recently used : 4 days with interpet number 8 anti fungus
Test results for ammonia, nitrite, nitrate and ph both from the tap and tank - all normal but temp has raised naturally to 22c

 

[saph.st24]

hi
sounds like the fish are losing their stress coat which is blocking the filter
probably caused by water quality and parasites
a anti-slime treatment and regular water changes add extra air remove activated carbon if you filter has it

 

[Anna Robinson]

If the water is cloudy and the fish are gasping that strongly suggests there is a problem with the water. Are you sure your ammonia and nitrite readings are zero? When you clean your filter, I assume you know not to wash out the media under the tap, as this will kill the beneficial filter bacteria?

In the meantime, you can't go wrong with large partial water changes while the fish look distressed. Ensure the new water is dechlorinated and roughly the same temperature, of course. I would not add any treatments or medications until you know for certain what the problem is.

 

[WILDER]

The poster did the same thread in emergency section and the tanks overstocked.

 

[saph.st24]

yeahover stocked and the filter isnt big enough either