Overstocking?

[lohpaul9]

My grandfather really loves to keep koi, so he has THREE of them plus TWO pleco and 3 mollies in a 15 gal.
The koi are rather small and dont think they're growing cos of the small tank, but all the fish are really energetic and dont seem to show any sign unhappiness. Is this tank okay long term?

[tetrakid]

My grandfather really loves to keep koi, so he has THREE of them plus TWO pleco and 3 mollies in a 15 gal.
The koi are rather small and dont think they're growing cos of the small tank, but all the fish are really energetic and dont seem to show any sign unhappiness. Is this tank okay long term?

Fish will be happy as long as they have clean water and enough food.

Restrictive living conditions such as tight space can inhibit optimal growth and affect the overall development of the fish.