When I first used my python I had a 75 gal. with around 75 fish/ 40 (PLASTIC) plants/ couple of fake logs etc.
I would change around 20 - 25 gals. a week. I'd clean gravel/remove water with it. I just threw the end out the back door running towards the plants outside. They seemed to like it. Then I'd hook it up to the kitchen faucet, take a floating thermometer and get it as close to the aquarium temp as possible usually a degree or to higher if anything. Then fill the tank slowly. Approx. 20 gph. Add chlorine remover at the start and some more when i was done.
The only fish i recall loosing for about 2 yrs. of that was a Kulli Loach... i came in the room and he was face first in the large tube swimming against the current. He seemed to be enjoying it, BUT, he was dead the mext morning. Sucked up too much chlorine, maybe??? You might wnat to remove the end for cleaning the gravel, to avoid any fish enjoying there self to death?
My mom has an INDOOR POND now. I do the same 'ol, toss the hose out the back door thing with it. But, i have a 30 gal. (plastic) trash can that i fill up first (after placeing it next to the pond) useing a floating thermometer to get it at temp. or above by filling it from the kitchen faucet.
And add chlorine remover right before its full. And use a small pump in the trash can to add the water back to the pond.
This could be used the same way for an aquarium, just need a big enough pump to get it that high is all.