Hello, sorry you are having problems with your fish. I'd like to back up the advice you are being given re 50% water change now and subsequent smaller water changes. This is by far the safest and least stressful way to help your fish.
Can you tell us your tank size, inabitants etc. What dechlorinater do you use and how do you use it? Have you had a recent powercut or anything which may have killed off bacteria? As you already know the tank is too small but daily small water changes should be keeping the levels down.

Probably for the best but hard nonetheless I'm sure. hope it all gets better soon. Is it just the one fish you have now Grim?

Depending how many pads you have in your filter, just do one at a time or if you only have 1 pad, cut it in half and replace half at a time. Filters should really only need to be cleaned etc once a month or so. Anything more would indicate the filter isn't up to the job.

Howard is spot on He does know what he's speaking about

I'm not sure FA, it's one of the two! I guess getting a new test kit is the best way to find out...!
The move was not too bad tbh. I just took out all of the decorations first, then about half the water, then put the fish in bags as late as possible in the process, then the rest of the water and removed the filter then set it all up again asap afterwards! It took about 2 houra from start to finish.

Just curious. My big Oranda has cloudy eye but all the water readings seem to be perfect (ammonia and nitrite 0) BUT what is making me wonder is that I have a very low reading for nitrAte, it's reading <5ppm on the card. I'm just about to do a 50% water change anyway as it's possible the water is a bit off due to the tank being moved into the house from my parents 2 weeks ago...

Sorry to hear you lost your fish after all that . You tried hard for him.

How regularly do you test your water? What and how much do you feed your fish? I think you've mentioned it before but could you run us through your usual maintenance routine also please? Thanks

ETA- I just read your other 'filter' post and am just checking... am I right in thinking you've just added another fish to the tank recently? How big is the new addition? It could be that the extra fish has increased the bioload and the filter is struggling to cope while it builds up more bacteria. Also, if you do have another fish, has your feeding routine (amount/regularity etc) changed at all?

I keep a bristlenose in with my goldies and he does very well. Mine are fancies and the water temp is kept at 22C so everyone is happy in the tank. If they are single tails (hence my first question) then no, I'd not recommend it as obviously single tails need colder water.

20C is an ok temp for fancies but I keep mine at 22C (sorry, I've said that a lot of time now!)as was recommended to me. The heater is still a good idea as it'll keep the temperature stable. I see my heater coming on quite a lot now it's colder outside and I'm glad it's in there to keep the water temp stable as fluctuations can adversely affect the fish.