To boost water hyacinths put them in a bucket with Miracle Gro or other liquid fertilizer diluted by half of what the label says. Let them sit a few days. Rinse them very well before you put them back in the pond. Do not just dump fertilizer in your pond. You'll be green in short time.

Being in UT, you might have some of the really super hard water that we have here in western CO and the water hyacinths don't like it. And/or you might have water that is high in salt. This prevents the hyacinths from taking up the nutrients that they need.
Also look at the roots of your hyacinths, perhaps the fish are eating them.
You can do the Miracle Gro treatments as mentioned above. You can also use Muriate of Potash

Yep, we have very hard water here and high ph. I tested the ph in my pond knowing hyacinths like water a little more acidic and my ph was over 9.0. I tested my hose water used to fill the pond and it is 8.0-8.5. I have been adding white vinegar to bring the ph down a bit and it is now down to 8.5. I will contintue to add white vinegar and hope my hyacinths snap out of it.

I trimmed all the brown off of them and have half sitting in a tub with MG since Tuesday but haven't seen a change in any if them yet.

Just be careful about trying to adjust your ph so you don't have wide ph swings and kill your fish. I found that it just seemed to be more of a headache to fight the ph than its worth. I leave mine alone but I don't have quite as hard water where I live now as I did a few years ago.

Hi
I think i'd recommend the opposite approach There are
a gazillion types of water plants and since your pond seems in good shape ,why not just grow those that do well??
Are your other plants affected?? What do you do with them in winter anyway?? Why risk upsetting the pond??
gary

My pond is small, only approximately 500 gallons. I have the same problem with my WH yellowing. I attribute that to water temperature being too warm in such a small pond. Although your pond is much bigger, could it be that the WH is in a shallow area and the water is too warm?

garyfla, I would go with that approach but it seems all my plants are struggling to an extent, not just the WH. It is just the WH that are looking the worst. I think my rocks are leaching into the pond causing a high ph (constitantly around 9.0) and the plants prefer more acidic contidions.

I don't have rocks all over in my pond, just around the edge in and on the falls. I have been treating the pond with vinegar, so hopefully over some time I can bring it down a bit.

I did add some stump rot over the weekend (hopefully that will give the plants a boost).

moonies, I don't think it is the temps. I heard WH like warm water.

Unless the rocks are made of lime stone they should not effect the pond PH. You can test them by pouring vinegar on them, if the area fizzes they are made of limestone.

WH in my experience do best in ponds with lots of nutrients some of which a first year pond lacks. My problem this year is the goldfish tear mine up when spawning in the roots and all the other fish including the golden orfes tear at the roots to eat the eggs. A plant has a hard time growing when the roots are half the size they should be.

I've had rocks IN my pond since it was built in 1996 and no problems with ph....no problems at all but that is another story.

Messing with ph can really harm your fish.

Water Hyacinths are native to hot tropical South America and have spread to tropical regions around the world causing massive problems in some waterways. Warm water and full sun should not be a problem for them unless just taken out of a box in the mail or a shaded area.

Fish can eat their roots and ponds that are new or have low fish loads or are scrubbed clean have little nutrients for them which is why soaking them in a bucket of Miracle Gro can really help....