Betta "respite care"

A thought, perhaps a far-fetched one, who knows.

My male betta has been lethargic for ages, although he is probably
just old. He prefers hot weather (loved 30C for some reason!) and
also responds to me, food and the missus in the adjacent tank.

However he has - and has had for ages - white growth in his fins,
not fluffy, and doesn't seem to be getting better or worse.

I was wondering if a spell in my 4ft tank, in a breeding net box
so he is safe, would help. It is a little warmer than his tank
(which is a stable temperature but a little cooler) and has
had no illness in the whole time its been set up.

The water in the Betta tank is changed regularly but I was wondering
whether the clean, warm water in the 4ft tank might be nice for
him, perk him up a bit and maybe his fin will heal? The pH is
similar, so is the salt level (very low) so there'd be no shock.

Might this help him? Or might it introduce disease to the healthy
tank? I'm not sure whether it would be a nice holiday for him!

--
Flash Wilson
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