Hi again,
Yep, good advice from Havelock *thumbs up*
Water parameters are definitely the thing to be the most aware of. Your temps and pH sound good, and I assume you're dechlorinating the water before you add it?
The gravel would be good to swop before he swallows any, although the pebbles look quite large luckily. They won't be causing him to stress out too much though. Sand is easy to clean - you can buy pump thingies at pet shops, and you can put a couple of snails in too to help you with this.
The fact that he's eating is very good! Axies tend to go off their food when they're overly stressed. They're less hungry in lower temperatures, so the fact that he's eating
and the water is cold can only be a good sign.
I personally don't know about mealworms. I buy frozen bloodworm cubes at the aquarium shop - they're less icky
. Every now and then I feed them either a sliver of duck liver (you can buy it at a butchers and freeze it) or non-fatty raw beef, and even the axolotl pellets from the aquarium shop are good.
Your set-up is good, don't worry! The filter is hitting the plant, so you've minimised that as best you can. I would suggest moving it away from the telly - like I said, the noise and the flickering light may disturb him. However, you're desk might not be optimal if you bump it with your leg or knees for example when getting up or sitting down.... I'd advise going to an op shop and getting a small $20 coffee table/side table that you could use soley for his tank.
Lastly (epic post this one!), his behaviour isn't too unusual. Like I said, mine were startled when I first got them. As mine is a big four foot tank, they'd swim swim swim them bump! into the glass until they learned the diameters. They were also startled by my hand near them when I first tried to feed them, and by my appearance outside the tank. Yours could possibly be seeing his reflection, but if he's anything like mine, he's actually responding to you! Mine now stop whatever they're doing when they see me and yeah, they move their hands against the glass, but not in a panicy way. It's as if they're as fascitated with me as I am with them! Plus, I am the bringer of food, and I think they recognise that *lol*
If I were you, like I said, just wait and see. Watch and try to determine if he's just randomly panic-swimming, or if there's anything that's setting him off. I would advise against changing the tank too much again for at least a week. If the water levels/balances are OK, and he's eating, then things aren't too bad!
Give him a day or more to adjust, and see if his behaviour settles down a bit. I know you want to change the gravel and the plants, and then maybe the water again after that
, but if he doesn't physically look sick at all, it might be better to wait and watch carefully and avoid stressing him further.
From my experience there's so much to understand and so many variables that you can send yourself into a tailspin trying to analyse what's wrong, when in reality it all might be fine!