when I first got into this hobby, about 15 years ago (I feel like an old man saying that), I would do 90% water changes. here's how it went:
- take as much water out of the tank as i can, leaving enough for the fish to swim/flap around in.
- take out all filter cartridges and violently spray the crap out of them w/ a hose until it looked new.
- stick hose in and fill up.
- add (forgot the exact name) stress/slime coating liquid.
surprisingly enough, i don't recall ever losing fish b/c of this
- take as much water out of the tank as i can, leaving enough for the fish to swim/flap around in.
- take out all filter cartridges and violently spray the crap out of them w/ a hose until it looked new.
- stick hose in and fill up.
- add (forgot the exact name) stress/slime coating liquid.
surprisingly enough, i don't recall ever losing fish b/c of this



