Pond Boss Forums INTRO Questions & Observations algae control without harming amphibians

Pond Boss magazine provides a lot of information about raising fish and controlling aquatic vegetation. I managed to feed and raise big bluegills, channel catfish, and bass in my mini pond. I also managed to grow a lot of cattails, Chara, and filamentous green algae. all was going great until late spring 2015. The weather was very warm, then cold, then very warm, then cold again. The result was 2 massive fish kills. Even my 19-pound channel catfish were killed. Only small fish survived. The water actually became nearly black due to the oxygen depletion. My pond had another fish kill in late spring 2016. The pond got black again due to oxygen depletion. I assume this is due to the die-off of the filamentous green algae. Now I want to use chemical warfare if necessary against the algae. I don't think I need to kill the Chara, just the filamentous algae.

The complicating factor is that my wife and I love the frogs, turtles, and other non-fish animals as much as we love the fish.

My question is: How can I kill the filamentous algae without disturbing the reptiles and amphibians?

Additionally, I want to limit the cattails to about 30% of the pond perimeter. How can I control the cattails without disturbing (killing) the reptiles and amphibians?

I hate to use chemicals of any kind but now I see no alternative. The pond does have a windmill for aeration but of course it is limited when there is low wind speed.

I have not re-stocked fish. There are no catfish remaining, only a lot of small and medium bluegills as well as some 8-10 inch bass.

Please tell me what you suggest I do. The pond is in central Indiana.

Thank you.

Sorry about the fish kills. They can be hard to take. You call it a mini pond but how big is it? I've been using blue pond dye and it seems to keep the algae to a minimum as long as I keep it dark enough. I still have turtles and frogs so I don't think it bothers them much. With fish as large as you had, is there a possibility the pond became way overstocked for its size and it helped cause the dissolved oxygen problem? As for cattails, I have a few and try to keep them confined to certain areas. This would take too much time if there are lots of them but I mix a little roundup in an empty coffee can and walk around with a cheap throw away foam paintbrush painting it on a leaf here and there, trying to get at least one leaf on every unwanted cattail. They die in a couple weeks. Good luck.

Controlling the vegetation won't guarantee against future fish kills. If your pond is really that mini, an aeration set-up won't cost much and would really help protect you.

The pond is 0.2 Acre with a maximum depth of about 7 feet, but much of it is about 3 1/2 feet. I know I ended up with too many pounds of fish per acre and the fish waste plus algae die-off depleted the oxygen. I am concerned about removing the bottom of the food chain (and starving the tadpoles) if I successfully kill the algae. I do have some pond dye but hesitate to use it for that reason. At this point however, I may not have a choice if I want to grow fish. A shallow pond like mine is great for growing fish.....if they stay alive.

When do you add pond dye? I assume it is when the water reaches about 50 F.

I use roundup to control thistle. I'll have to give that a try, at least where I can easily reach the cattails along the shore. I'll have to be very careful not to get a drop of it into the water. I hadn't thought of that so thank you for the idea. I like a lot of vegetation in and around the pond for species diversity but it has gotten excessive.

Yes I know but I hate to invest in a second aeration device before trying vegetation control first. Part of the problem is running power to where it would be needed. That is one reason we purchased the windmill (instead).

Hi Fred,

Roundup is not to be used near your pond. There are many pond safe glyphosate (same as Roundup active ingredient) herbicides on the market such as Rodeo that would be a better choice and getting a little in the water won't hurt.

Good Luck!

I've run air to a pond over 1,000 feet away through buried poly pipe....

Treat the cattails now, when water temps are dropping in the Fall. That is the most effective time to treat the cattails, and the amphibians are starting to go into hibernation and are MUCH less active.

Yes, you cannot use Round-up, other glyphosate based chemicals or for that matter ANY other chemical on or near a pond where the chemical can get into the water if it is not specifically listed on the label as a chemical that you can use on or around a pond/lake/stream, etc. Don't forget to add pond use labeled surfactant to the mix when spraying the cattails. I would also cut off the cattail seed heads now and dispose of them in the trash or burn them. No use in killing them and leaving all the seeds to sprout next year.