There are several things that can cause yellowing in water lettuce and hyacinth.

First, water lettuce does not like hot sun, so if your pond is in full sun, that could be an issue.

Another common issue for the floaters is lack of nutrients. You might consider removing them from the poind and letting them sit in a tub of Miracle Grow for a few days. Once they've perked up, rinse off the roots and move them back to the pond.

A third issie is the fish themselves. If you have koi, they will eat the roots, which in turn prevents the plants from absorbing their nutricional needs. Goldfish are less likely to eat the roots.

Thanks for the info Nancy. I talked to the guy at the "pond place" near my house and he suggested I buy some nutrient tabs. I was just afraid to add more nutrients to the water since I had bits of string algae forming and was afraid that would cause a bigger issue. Your idea of Miracle Grow seems like a good one. I have to say though, it could be any, and all of the reasons. I have 4 koi and a full sun pond....hmmmm
Again, thanks!
Melissa

I haven't had any luck with either WH or water lettuce until this season. I thought I had tried everything. Didn't even buy any WH this year. Dropped the lettuce in a pot I normally use as a double pot for taro but hadn't put any in yet. The lettuce looked pretty sad but to my amazement it recovered in a hurry. At this point the original is ten inches across and it started at four. The entire cashe pot is full from three plants and overflowing. One plant was pushed out from overcrowding. We'll see how long it lasts.

I would have not even thought to do that, sleepless. Thanks for the idea. Glad to hear it is working this year for you...sounds it's worth a try!

I've never had any luck with water lettuce--goes yellow and brown around the edges. My pond is in full sun until about 6pm then gets on the south end finally. I grow parrot's feather instead as I can anchor it along the edges under rocks. Don't have to worry about it going in the skimmer. With our cold springs we've been having the water lettuce just doesn't like my pond or me.

I buy 3 water hyacinth and 4 water lettuce and within 30 days, my 9' x 6' base pond (with 7 goldfish), my 4'x5' upper pond and 3 tier waterfalls are completely full of them!! They seem to clean out any string alge and filter the water before it hits lower larger pond. Definitely get some fish and let the plants clean the water. Last year I threw away 3 13 gal trash bags of these as they overtook the ponds.