I will probably cause a bit of trouble over this, but here goes anyway.
I find this practice to be very inhumane! I am appaled that this is still in practice!
Nine times out of ten, the plant is not properly maintained; the water is not kept changed on a regular basis, there is little fresh air for the beta to breath, and there is very little space foir the fish to move about freely.
Being realistic, I know people will continue this practice until it is totally outlawed, so let me add this piece of advice - DO NOT use Water Hyacinths!
Water Hyacinths require very high light, direct sun, in fact, in order to live and grow properly. This would heat the water to levels that would litterally cook the fish housed in such a set up.
Water Hyacinths do not make good house plants; they don't even do very well as aquarium plants because of their high light requierments.
Nature is trying very hard to make us succeed, but nature does not depend on us. We are not the only experiment.
- R. Buckminster Fuller