| Welcome to the forum,IrishCreamCoffee.
I think you could use the water for plants that grow in soil since the ammonia can bio-degrade in the soil( facilitated by bacteria in the soil, I'd imagine). I assume that no other chemicals are used as water treatment in your aquarium.
From the picture I see you have cold water fish (Ryukins/shubunkin/calico/goldfish) which are notorious for high ammonia build-up, since they excrete a lot. Additionally you probably have the temp set to about 20C (72F) or less for them that does not allow ammonia to escape. I would not recommend the water either for orchids or any other indoor plants.
Just out of curiosity what size tank is it? Do you have a good filter? You mentioned changing water 'many times' per month. That is too many water changes unless you have a small tank and many fish. If you have a 35G tank with about 3 pairs of ryukins and one or two plecos( I see you have them), the water change should not be more than 2 per month with a good filter.
Goodluck.  |