I have a 55 gallon tank and do 5-10% water changes at least once every 2 weeks. I hate to waste water so I was wondering if it would be ok to use this water to water my orchids. There is no salt in the water. Seems the fish waste int he water would act as a fert but am I overlooking something that might be a problem?
It's fine. Just make sure the water isn't really disgusting. Some plants don't like that, but for the most part this shouldn't matter for many of the commonly grown plants either.