i have a 600 liters aquarium that is sit outside near my garden with 10 fancy gold fish
it is powered by canister filter as mechanical and biological filtration, and a air pump to aerate the water
i added 1.5 meter 3" wide pipe and made 8 holes for cups (to plant inside it)
i make a lot of holes at the bottom of the cups and added to it some tomato and pepper plants
the water goes from the aquarium to the filter and then to the pipe and then back to the aquarium
it was working fine for a couple of weeks and then it starts to die (roots disappear and leaves turns yellow)
the roots never go outside the cups and for some of the plants (only 2 that still available) the roots coming back and die and so only
the plants never grow up
i am not sure what is the problem, and i am afraid we have less oxygen in the pipe due to bacteria in the filter, or little nutrient
one more thing, i used to have a lot of algae in the aquarium and now the water is clear

please advise