Hi, I have an 18 Gallon (cofee table fish tank) it has been set up for about 2 months. everything was fine, tested everything weekly with no problems. I have been doing 10% water change once a week.
Last night the water has gone really cloudy and the fish are struggling to breath.
I have done a 50 % water change last night and a 25% water change this morning. I have just had to do another water change as the fish were all vertical again struggling for air.
Once I have done the water change everything seems fine for a while and then it deteriates again. I fear with all the water changes the balance in teh tank is now gone but without changing the water they are struggling to breath. (there has been 1 fatality already)
The only thing we can think of that has caused it was that the water out of the tap was very cloudy the other day and there was something in it that is now breeding in the tank.
we have added oxygen tablets to no avail???
All Nitrates Nitrites, PH, Amonia etc are all fine!
I don't know what else to do I have tried bottled water (with tap safe etc etc)
All I keep getting told is to do a water change but this has been done already and is just temporarly solving the problem.
There also seems to be an oily film on top of the water, I don't know what this is any advice on how to remove it safely would also be good
Any help would be greatly appreciated
Sorry, we have 5 fantail gold fish all different types
their is also a air stone in the tank, no plants, a few small rocks which have all been in from the start.
PH has dropped from 7.2 to 6.8 I can only assume it is from teh water change.
we feed the fish every other day at the moment
filter system is :
carbon filter > coorse sponge > bio balls > fine sponge > fan