Algae in a small pond - okay?

We have a bathtub-sized pond that I dug a few years ago in the middle of our garden, fed entirely by rain. We love it as it attracts pollinators and frogs, and is also just fun to gaze into.

This fall I noticed a lot of green algae growing in it, that I don't think was there in previous years. (Photos pending; need to get them off my phone.)

Should I be concerned? And if so, is there anything I need to do about it?

[mods: please move to "ponds" -- I was looking for that topic but couldn't find it!]

Hi Ned,
Some algae is to be expected in any water feature. It can become a problem if it overwhelms things. The smaller the body of water, the easier it is to get out of balance. I don't the best method to deal with the algae, but I wanted to mention that you will probably need to periodically treat that water. A swimming pool sized pond would have more leeway, and a half acre pond even more.

So, with a small pond like you are describing I would not think it would take a lot to get an algae bloom. I wouldn't be worried too much because it is hard to control water quality with such a small pond in my opinion.

Algae is blooming because of the presence of nutrients in the water. Runoff potentially. If you can control how the nutrients are getting in, you can stop the bloom.

Perhaps looking into a solar aerator to for the water might help disturb algae spores but I don't have any first hand experience.

I think you can surface skim it and feed it to chickens, or compost it

Thanks for these replies, everyone. I think my next step would be to see how feasibly I can skim the algae, then if that fails I'll consider a solar aerator (provided such a device would not deter frogs). Before I do any of that, though, I want to verify whether I have to do anything at all:

It can become a problem if it overwhelms things
[...]
get out of balance

A problem for whom? Out of balance for what? Do pollinators/frogs/etc. depend on the pond being algae-free?

Hi Ned,
The biggest reason I know, is that too much algae can use up the oxygen. This causes problems for fish and invertebrates likes frogs. Could a frog jump in and out with the algae? I don't see why not. But they are not going to stick around if they can't absorb oxygen from the water. I don't think you said you have any fish, but lack of oxygen is going to affect them as well. If the water gets too stagnant, I have seen nasty types of algae and microorganisms move in, which cause stink and in rare cases produce poison.

Ned does your pond overflow, or does it tend to empty by evaporation. I tend to agree with those who suggest your pond has ended up with too many nutrients first off, so flushing it with extra collected rain water might be a simple fix that shouldn't bother the frogs.

Consider adding a pond weed that you specifically harvest for compost/mulch/animal feed as a way to keep the nutrient level from building? Former owners built an ornamental pond here which I don't have time to maintain to perfection, but duckweed showed up and I use it for that purpose.

Matt McSpadden wrote:Hi Ned,
The biggest reason I know, is that too much algae can use up the oxygen. This causes problems for fish and invertebrates likes frogs. Could a frog jump in and out with the algae? I don't see why not. But they are not going to stick around if they can't absorb oxygen from the water. I don't think you said you have any fish, but lack of oxygen is going to affect them as well. If the water gets too stagnant, I have seen nasty types of algae and microorganisms move in, which cause stink and in rare cases produce poison.

Jay Angler wrote:Ned does your pond overflow, or does it tend to empty by evaporation. I tend to agree with those who suggest your pond has ended up with too many nutrients first off, so flushing it with extra collected rain water might be a simple fix that shouldn't bother the frogs.

Consider adding a pond weed that you specifically harvest for compost/mulch/animal feed as a way to keep the nutrient level from building? Former owners built an ornamental pond here which I don't have time to maintain to perfection, but duckweed showed up and I use it for that purpose.

Thanks, this is excellent info & suggestions.

- We don't have fish;
- The pond does overflow in heavy rains but also tends to evaporate quite a bit (3-6 inch drop in water height is typical) during drying-out periods.

I wanted some outdoor chores this week, and it seems I've gone out and found some! I'll (at least try to) scrape the algae off and put it in the compost, and I'll flush it with one or both of our 55gal rain barrels.

Lingering question in my mind:
If the algae eats the nutrients, the algae must be pretty nutritious. What eats the algae?

Is visiting a lake and collecting differing waterplants in a bucket an option? Bring thèm home and into the pondy they go. Most wont make it, but normally some variety of plant will stick around and collect the nutrients your algae eat in a more efficient way. They'll starve the algae and create oxygen by day which will enliven the algae eaters you've caught in the lakewater.

What eats algae in a pond?
6 Best Algae Eating Fish for Ponds - Nualgi Ponds
The best algae eating fish for a pond are Koi, Channel Catfish, Chinese High-Fin Banded Shark, Flying Fox, Pond Loach, and the Japanese Trapdoor Snail. After our interviews, research, and trial and error, we recommend the following inhabitants to help you manage algae in your pond the natural way! May 15, 2019

That is Googles answer.  So gold fish with an aerator or pond fountain  Will make your pond more interesting and balanced.  My sister used to keep a gold fish in each watering tough to control algae and mosquitoes and they lived there for years without any maintenance.   You can just buy the inexpensive ones sold to feed larger fish.