Hello all, I have a problem with this yellow floating heart. I have used shore clear in previous years....problem is it turns brown and you still have to pull it out by hand. Is there anything out there you know of that will kill it? any chemical I can add to make the water so toxic that it will kill this crap? thanks, Jeff

Welcome to PB.
The reference to making "the water so toxic" is a gross misnomer. The principle behind using herbicides for the management of aquatic vegetation is to target the offending plant(s) with little or no collateral impact. I'll skip a treatise on the subject since that wasn't the purpose of your post.
Back to your question. I'm not intimately familiar with yellow floating heart (which is an exotic invasive species), but I've dealt with many of its cousins.
Clearcast or Imazapyr are relatively effective treatments for most of the floating heart species. However, eradication may not be possible once this genus becomes thoroughly established and entrenched; which means that "management", through multiple means (including herbicide treatments at regular intervals), may be your only viable option.

Aquathol K at 1.9 gals/acre foot plus Hydrothol 191 at 0.5 gals/acre foot has been effective at controlling the floating heart species. However, as Kelly mentioned this is a very hearty weed and you will likely have to do retreatments. I have seen through active management (several retreats) of this species that densities can be reduced to very small patches. Then you might be able to physically remove plants that remain.

You might consider cutting some of them where you want open water, and leaving the rest to look pretty/let the fish hide. The Jenson Lake MowerTM, along with its rake to remove the cuttings, is a one-time expense that you can use whenever you need to. See lakemower.com

Sounds like a decent product..