Question
I have an indoor pond, about 180 gallons, located in a skylit atrium. I have six Comet fish, and had six water hyacinth plants. All the roots have either fallen off the water hyacinths, or they were eaten off by the fish. Not sure which, but they have been continually plugging the foam filter. As a result the plants are not healthy.

Answer
Your problem is not uncommon in outdoor ponds.  Goldfish will eat the roots off.  They can also fall off.  If the plants are dying off, you can try adding some liquid plant fertilizer.  They should get enough light if you have an atrium.  What is the temperature?  You can protect the hyacinth from the fish with a floating mesh island, etc.  A filter with a larger surface area over the intake will reduce how often you need to clean it off.  If the hyacinth die off enough, you may have to toss them.  I hope things improve!  My water hyacinth outside are doing poorly this year, for the first time in 9 years.  Coincedence?  I don't know but others have reported the same thing.

Robyn
fishpondinfo.com