Maybe my plan to add a low density of both species + RES this fall is a good option? The FHM (and/or GSH) seem to have produced a lot of fry. I have had a hard time finding eelgrass in local water but found a couple plants last night and put them in the pond. Hopefully they will take. My two tries at getting purchased spiral eelgrass to take in more established waters failed in the past. This may have been due to crayfish, but who knows?
