Can u give marijuana plants water from a fresh water fish tank?

I heard the shit from the fresh water in the fish tank would feed the plants if u put some water from the tank. I have frogs and guppies. The frogs eat blood worms and the guppies eat flake food. Would any of those stuff will be bad to water my plants? I also have a filter thing for it.

Yes you can, and it works pretty good. I haven't used it myself, but my friend has, and at the very least it isn't going to hurt them. Kinda hard to know how much nutes they would be getting though.

My two cents.

my parents have a pond and they use the water in there garden.... very high in nitrogen from all the fish piss and shit

Hell yes you can! Not only does your tank water have nutrients but it also has loads of beneficial bacteria that are responsible for the nitrogen cycle if you grow in soil. In a hydro system it's a great way to add micro-nutrients that may be absent in many commercially available mixes.

I have a friend that does this and it works really well... The plants act as a filter for the water by eating up all of the nitrogen and such and then the water is drained back in to the fish tank...

I used to live next door to a trout farm. They had to pump fresh water for the trout then they just ran the water out on to their fields and their crops were all the best around.

fish waste has a lot of ammonia in it. you can use it but i wouldnt.