Blender disease

Hello
I bought gold laser Cory 8 days ago and today I found him up side down .I will change today 50% water and will maintain my tank(clean gravel ,glass ,filter )

Just wondering should I put gold Cory in isolating tank ?
I have spare 20l tank
Should I use salt and blender disease medicine .
I know I need heater but do I need filler and air stone ?

Thank you for your help

P.S.
Water changing 70l every 2,5-3week
30l every 1,5-2week
My tank 150l
Have fluval 207 fillter
Heater set on 28
Temperature 26-27
Have 2 air stones
Have live plants
5 amano shrimps
Female beta
2 baby female beta
2 balloon mollys
3 balloon baby molly
2 platy
7 Cory fish
in picture this is water readings I will change 70l today .

LOL blender disease, that's a good one
I assume you mean swim bladder disease.

Post a video of the fish before you waste money on medications that won't work. Upload videos to YouTube, then copy & paste the link here.
If you use a mobile phone to film the fish, hold the phone horizontally (landscape mode) so the footage fills the entire screen and you don't get big black bars on each side.

Corydoras regularly take in air from the surface and it travels through their digestive tract (intestine) and gets farted out. If they swallow too much air, they can float about for a while until they fart the excess air out.

If a fish floats to the surface when it stops swimming, stop feeding dry food for a week and use frozen or live food instead. If the problem fixes itself after removing dry food from the diet, then the problem was air in the intestine and you should minimise dry food and use more frozen or live food.

If a fish sinks to the bottom when it stops swimming, then it has a swim bladder problem and there is no cure, regardless of what pet shops say, and the fish should be euthanised. However, before killing any fish, post a video so we can check it and confirm the problem.

Most catfish don't have a swim bladder so the Corydoras probably just has air in its gut. Some fish regularly swim upside down or rest upside down.

8 days ago is still in QT timing, and it's unfortunately normal to lose fish in the early days after arrival. QT now would be too late - if it's something that spreads, it's out there.

That heater is set extraordinarily high for Corydoras. 26 is stretching it to the limits for most. If you can get to 24-25, everything will work much better..

GaryE said:

8 days ago is still in QT timing, and it's unfortunately normal to lose fish in the early days after arrival. QT now would be too late - if it's something that spreads, it's out there.

That heater is set extraordinarily high for Corydoras. 26 is stretching it to the limits for most. If you can get to 24-25, everything will work much better..

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Except the betta's won't be comfortable with that. Maybe they could go in the 20l tank at 26c?

Betta splendens is actually in a range from 24-30 in nature, and I found keeping them warmer accelerated their lives considerably.