Thanks!
I've had goldfish for some years now, and found that plants are great for absorbing a lot of the nitrate (although not all). I still do quite a lot of water changes, to remove it, but the plants seem to take some too.
I have a few more tanks, for the smaller goldfish, and they too have fast growing plants on the surface. The reason why I can't have many plants bellow the waterline is, that goldfish will eat them. They will even nip on the roots, so many of the plants are placed in plastic baskets to prevent the fish from eating too much of the roots
