Roundup might be a bit drastic on a water plant, particularly for other life forms in the water. But Water Hyacinth is a serious weed and prohibited in a lot of areas. In places where you're allowed to grow it there shouldn't be a need for fertiliser. What's in pond water should already be enough for it. If the plant's not doing well there might be other issues with it.

m.: ROF LOL

Hmmm... I think you mean to help them grow, not eradicate them correct? As far as I know there IS only one type of Miracle-Gro - the blue powder stuff that you mix with water. There are now many types of Miracle-Gro products - everything from potting soil to actual plants that bear the Miracle-Gro brand - but the all purpose water soluble plant food you want is still the original stuff. I think they make an organic version - not sure I would pay the extra price for something that I wasn't going to eat, but that's up to you.

Thank you, that is the kind of Miracle-gro I am trying. I have a pond with a BAD algae problem. It seems healthy, it doesn't have a bad smell, in fact no smell at all. All we have seen are mosquito fish and baby goldfish. What lurks below the algae is anyones guess. No string algae just pea soup green. I know that the fact there is no real shade yet( we have a triangular sail shaped canopy from Costco over part of it) and 2 pumps one with an anti algae lamp in it. I know enough to not let the water hyacinth ever get into any streams but I want to see my pond clear up. This is so frustrating. We are in Hawaii so there is lots of sun. I had a pond before but I started that one in the fall, it was clear. There were goldfish, guppies, mosquito fish, and even some angel fish.

Don't put Miracle Grow in your pond. The plants will be fine without it. Patience, it will clear up eventually. Miracle Grow will also feed algae, and you don't want that either.

I'm not adding Miracle-gro to the pond instead I have my water hyacinth in a bucket with a solution of Miracle-gro. I had read that if you don't have many fish ( make that hardly any but who knows - can't see them) that the water hyacinth need nutrients i.e. Miracle-gro.

Carla, if you have pea soup green water, the algae is eating the nutrients in the water. If you put floating plants on the top of the water, like your water hyacinth, the hyacinth will eat the nutrients instead of the algae, and the algae will die off. Water plants will out compete the algae. You have nutrients for your hyacinth, or you wouldn't have algae to being with.

Water hyacinths frequently struggle in ponds for a variety of reasons. I can grow them in my patio pond and my pondless waterfall, but they will die if left on their own in my pond. So I rotate mine in and out of the pond, replacing them with plants from the other two locations to keep them all healthy. But if that's not an option, some people find a soaking in a solution of Miracle-Gro will help perk them back up.

They also like being crowded together - for whatever reason they grow better when they are in cramped surroundings. Some people use a hoop to corral them or some other way to restrain them. Fish can also be hard on them, as they love snacking on the roots. I've seen hoops with nets in them used for floating plants - the plants are in the water but the fish can't get to the roots. (One caveat- I read about a ponder who lost a big fish when it jumped into the hoop and couldn't get back out. )

When we first started our pond I was so excited to get water hyacinths and water lettuce and watch them take over my pond - every one said they grow like crazy. But for whatever reason, they just don't like my pond. And I've since learned that's true for lots of people. These are both invasive species which are being banned in more and more states. I have a feeling it won't be long before we can't buy them at all.

How long do you leave them in their "protected environment?

Until they green up again and start growing. I'm probably moving hyacinths around once a week or so. Like I said, I have them in three locations - in my patio pond they do well, in my pondless waterfall they do great, in my pond they struggle. So I have them in rotation accordingly. And by the way - it's all the same water. We fill both the pondless and the patio pond from the big pond every spring. The only difference is the fish, so I assume they are the culprits.

They won't do well in my pond unless I shake out the roots every morning. I've found that the roots collect junk and act as a mechanical filter. But then they can get far to clogged up and not be able to take in nutrients. Getting clogged with Algae is the worst. That's why they like to be clumped together. Because algae get's stuck on the roots and then not being shaded by being clumped together the algae just lives on there stealing nutrients. Since I started clumping them together more, shading the roots better, and shaking off the accumulated junk on the roots they seem to be doing good.

There is ALSO LIQUID MIRACLE GROW DUH!

I wouldn’t use regular Miracle-Gro directly in a pond, especially one with fish. For water hyacinth, use a fertilizer specifically labeled for aquatic plants and follow the recommended dosage. Water hyacinth can grow quickly, so good pond water quality is also important. If you’re maintaining a pond with these plants, Aqua Ultraviolet has pond water-treatment and UV solutions that can be part of a broader pond-care setup. The key is to keep nutrients balanced so the plants grow without encouraging excessive algae.