Hi I'm new to this forum. We have a pond that for the most part looks really good but when the weather is hot in the summer, here in FL, we get this brown stuff on top of the water. We can't figure out what it is and wonder if it's toxic. It seems to be only in the summer when it's hot.

to the forum, @Lilcee! So sorry that nobody has answered your question yet.

I think that's just a form of algae, which is an aquatic plant which grows profusely in ponds when the water warms up.

Yes, I was hoping someone more local to you could help. Usually algae like this is harmless, but sometimes, and especially regionally, you can get toxic algae blooms, or more commonly cyanobacteria. This doesn't look like anything toxic I recognize, but if you're really concerned I would recommend reaching out to your local extension office, who should be able to tell you about anything toxic endemic to your area.

In a healthy ecosystem, it should clear itself up eventually, as the water rebalances. Even natural blooms are usually temporary. It sounds like you've already identified a seasonal pattern for it. Do you have fish in the pond? Fish are generally more sensitive than you are to toxins, so if they're okay, you probably are as well. Cyanobacteria, for instance, kills everything it touches when it turns toxic.

And, welcome to the forum! Thanks for the pictures. Hope to see more of you.

Thank you for your response. We do have fish and turtles in our pond and they are doing fine. It seems like when the weather is cooler the brown stuff goes away