Question: Lack of Oxygen? Cycling Process?

Hi all, I'm hoping you can offer some advice..
I've been down to my pet shop numerous times in the last month to try and sort this out but I feel like something is always wrong..

My (family's) axolotl is 12ish years old. He has always been fine, happy, normal, low maintenance. Even though he has been around this long it was not always my responsibility to look after him so I'm really like a beginning and struggling to understand this stuff!

One day he stopped eating food so I knew something was wrong. Turned out I had ammonia and nitrites. I done a big water change as per their instructions, and gravel clean etc. Within a week or so, the nitrites had built back up, so I kept doing around 25-30% water changes with DEchlorinated water (I use prime conditioner). He seemed to be getting better and started eating food again.

About a week or so ago, after a water change, he was going completely mad.. moving around the tank like I had never seen. I panicked and went to the petshop.. turned out my PH was low (must be my tap water?) and he said he will be fine just use some PH up powder... I've done that gradually, to try and bring it up because I read it's bad to have a big change in PH. Its around 6.8 now.

He hasn't been moving frantically, but he has been a lot more active then he ever has (but this could be due to better water conditions since the old water was not all that clean?) ......
What is worrying me is he is coming to the top to gulp air a lot more than usual!!
I would say at least 5 times an hour...... when I got an ammonia test a week ago, there was none. There is no nitrites.. I've done partial water changes today and yesterday just incase ammonia was present but there has been no change.

It seems like there is a lack of oxygen?? .. I have an air stone in there, and I have also recently installed a filter (which he may not be use to as there hasn't been one on there for a while) ........If anything I would have thought there is more oxygen in there than ever before...

I've read he may not be using his gills as much for some reason and substituting with gulps.. but why? .. I thought he looked a little paler in colour than usual.. and one side of his gills seems shorter than the other......

I just don't get it.. I have no idea if the tank is cycled, or what could be causing his lack of oxygen .. please help

Some more info:

Water parameters just tested..
PH: 7
Nitrite: 0
Ammonia: less then 0.25 but just done a water change with prime conditioner
Temp: 20 (always has been)

I really have no idea how to tell if the tank is properly cycled..
I recently added a new filter 2 weeks ago (low flow with a spray bar)
I have an air stone.

What I have just noticed is.. I have added API stress zyme as per the instructions of the pet shop to 'help with the biological filter' this was a few weeks ago, and just whilst doing my water change right now I've noticed hundreds of little LIVE BACTERIA I am guessing ?? SWIMMING around....Is this causing my axolotl any problems? .. I kind of want them gone but don't want to do too many water changes..? Advice?

Do you have gravel on the bottom of your tank? Get rid of it. Even adult axies will accidentally eat it, it may cause impaction and ultimatley death.
Stop adding pH down or up chemicals - axies don't react well to chemicals as they can absorb it through their skin. Water quality can be maintained with water changes, you shouldn't need chemicals unless it's on the advice of a vet.

Then you need to read up on tank cycling - you need to test for ammonia, nitrite and nitrate to see if your cycle is working. You should have ammonia = 0, nitrite = 0 and nitrate < 40 for a good cycle.If you filter is new it probably won't be cycled yet. There is plenty of info out the on the internet.

You cannot see bacteria - they are microscopic and cannot be seen with the naked eye. What you may have is some type of microfauna - coepepods, daphnia, planaria - if you post a picture we may be able to help you identify it. It is most probably harmless.

If your water quality is off it may be why your axie is going for air. But you also have to remember that warm water contains less oxygen than cold - you need to try and keep your tank cool in the hot weather. Breathing air is normal for axies, and I don't think 5 times an hour is excessive at 20C.

Thanks so much for your replies!!!

I do have some gravel in there.. around half.. he has had it for 12 years.. I was going to take it out (did start to) but I read somewhere it will disrupt the cycle and that's the last thing I want because this has been so stressful lol...I've tried to research the cycle as much as possible but its hard when everyone says different things..

I now have 0 ammonia (once I fixed the tiny amount I had, he has been breathing normally with no frequent trips to the top, Yay.. Whether it was related or not I do not know.. but I'm glad it has stopped)
PH is still around the 7 mark. (It seems to go down with my water changes so could be my tap water..)
0 Nitrite.
I unfortunately don't have a test for Nitrate ..

Anyway, he seems to be doing much better, and is always hungry so that's a good sign.

The newest thing is all of these tiny white tank critters - I panicked they were parasites, but after heaps of googling, I think you were right they must be some type of pods.. Unfortunately they are too small to take a photo of as I don't have a super camera.. They're tiny white dots that swim around and mostly rest on the glass and water surface. None on my Axolotl though which is good. He seems un-phased......

Are pods a good thing? Can they have any adverse effects on my Axi?
There were literally hundreds all of a sudden .. I did wipe some out when I didn't know what they were.. some others were taken in water change so there is less now- but still a fair few .. Suggestions??

THANK you!!