Illness/Sickness: Axolotl not doing well

I've had my axolotl for almost 3 months, he was doing fine for the first 2 months, then he stopped eating so well and only ate if I held it right in front of him, then he stopped eating anything and started floating a bit so I put him in the fridge. He seemed to be doing well in there so after a couple of days I took him out and let him adjust to room temp and put him back in the tank and he started swimming around and swimming to the top and gulping for air. I've got a 100l tank with an aqua one 102f filter with the arm attachment facing the glass. The ammonia level was 0, ph was 6.4 which I think is a little low not sure of temp or nitrate. I change 10% of the water every week.

I put him back in the fridge for a few more days (changing his water every day) he seemed to be doing OK so I took him out again today and let the water adjust to room temp and he started swimming around in the container and gulping air and his gills started looking discoloured. (when I bought him he has 3 gills on one side and only 1 on the other). I don't know what's wrong or what to do? Please help!

If he's fine in the fridge with daily water changes, but not in the tank, it must be a water quality issue in your tank. If you pH is low it's usually a build up of nitrates and nitrates.

I'd suggest more frequent water changes, maybe 10% 3 times a week or 20% twice a week.

And you really need to check your temperature - loss of appetite is often linked to a temperature spike. My male got heat stress this summer, it took him weeks to get his appetite back.

First off, what is "room temp" for you? Axolotls are more comfortable in 20C or less. That being said, it could very well be that your axolotl is stressed because of heat. This isn't really related, but it could help with your pH and nitrate/nitrite problem. Change 20-30% of the water instead of your usual 10%, this should help balance out the levels a bit more.

Thanks, I'll try changing more water and buy a thermometer to keep a better eye on the water temp, the weather here has been very hot lately. How long can I keep him in the fridge for?

I know a lot of the Australian members here will keep their axolotls in the fridge for a few weeks at a time. I think as long as the fridge is about 4 or 5C or above (correct me if I'm wrong, anyone), it should be fine to keep your axolotl in there for up to a week or so. You'll want to get a fan, or some ice bottles ready to keep the water in the tank cool, as well.

I think maybe the water was too warm, I've now checked Nitrate and Nitrite, both were 0. Ammonia is still 0, ph is still 6.4 or 6.6 (cant quite tell the colour). He seems OK in the fridge still, his gills have returned to a good colour so I guess room temp was too hot. I tried putting a fan on the tank but didn't seem to do too much, any suggestions on methods to cool the tank?

Like I said, get some ice bottles. Just get some decent sized bottles of water, dump out a little bit of the water, and freeze. If you get some extras, you won't have to wait for the ones you used to freeze again before you can put them in the tank again. Since you're in Australia, it's very highly recommended that you invest in a tank chiller as well.