I am new to ponds, we purchased this property about a year ago. it has a pond that is a little over 1 acre and about 18' deep at its deepest point. I need some help getting things into balance. the pond has a marsh at the incoming and out going ends. when there is steady rain things stay good. but here recently we have been without rain and the temps are in the high 80s. now we are starting to get a green film across the top. I added grass carp a few months ago to take care of the submersed algae and they are doing a really good job. but from what i have read the only option is to aerate the pond. it just seems so expensive to do this. there has a be a better permaculture way.
Up to a point algae are good for a pond...they are a sign of a productive ecosystem and are the base of the food pyramid. Provided there is a fully stocked ecosystem in the pond with fish, insects, amphibians, etc. most ponds can "bloom" with algae once or a few times a year to no ill effect. The other organisms will use the algae for food. Unfortunately North America in general is depauperate in filter feeders....fish that rake algae through their gills and use them directly as food, like the Asian carps (unfortunately illegal and invasive in most of N.A. now.....and a huge underutilized resource where found) I think there is one native filter feeder called the buffalo fish, but it might be hard to find them for stocking. But minnows of lots of species will help.
The sign of too much algae is fish gulping near the surface, especially early in the morning when respiration by both algae and other things has depleted the dissolved oxygen overnight. During the day, the algae and other water plants produce oxygen via photosynthesis. Adding submerged and floating plants to the pond will compete with the algae for nutrients. On a small scale, running a fountain pump with the pump enclosed in a fabric bag will act as a filter.....pull this out and rinse it out once a day. But this is for a small garden pond...
A bottom diffuser aerator really isnt particularly expensive, either to purchase or especially to run daily.
I reccomend a Vertex bottom diffuser run with a simple Gast air pump. Surface aeration is a totally different animal, that uses much more power.
The beneficial results will go way beyond reducing the algae. Your water will be more alive and 'liquid'. Hard to describe. Reminds me of the way that Biodynamic stirring alters the structure of the water in a way that makes is more beautiful and alive.
And I reccomend this often here at permies, but the forums at forums.pondboss.com are excellent and friendly. Not permie in their general outlook, but those guys know their ponds.
@adam would i need to run the aerater 24/7? i know what you mean with biodynamic water. that is not what my pond looks like right now.
@renate we do have upstream and up hill nutrient flow. i am working on collection swales along the hills that i own to try and slow some of the nutrients. i think the main thing is the lack of movement in the pond right now.
we have lots of fish in the pond and they seem to do really well. i dont think its starved for oxygen just not attractive and it doesnt seem balanced quite right. like a garden full of bad weeds.
No, I dont think you would need to run the aerator all the time. I typically run mine in cycles. You dont want to just turn it on and run it 24/7, it circulates too much water and induces too much chemical change in the water too quickly. What you would do is run it for 2 hours a day, then 4 hours, then 8 hours, then 16 hours, then 24 hours. Continue running it 24 hours a day for 4-5 days, then turn it off for a week. Hope that makes sense.
All in all, you might end up running the pump 1/3 of the time to get your results.
The bottom diffuser aeration does more to circulate your water than to aerate it. Like turning a compost pile, too much of a good thing isnt a good thing anymore. So circulate some, then let it settle again.
Circulating the water in your pond increases the pond's metabolism, so that the excess nutrients get used up rather than stagnating.
hope that helps, any other questions feel free to ask-