Would internal parasites make a puff who has looked very healthy for the past month bottom sit and be very inactive? My params are good and i did a huge 90% water change just in case. he has gotten very dark in color and is breathing deeply. What can i do Hes my favorite of all my puffs

It's really hard to tell from just that, off color and sitting on the bottom is common for puffers sick from many things. Loosing weight quickly and loosing the "food belly" very quickly, as well as stringy, waxy off-white poo are the strongest indicators of parasites.

I lost him

Oh dear, I'm sorry.