Natural Algae Control Advice - 2 year old habitat pond complex

[stu]

Hello all,

Background

I have a two year old habitat pond at our place in West Sonoma County. As you can see from the photos, the pond complex consists of: a small ~10'x10'x3' pond that was here when we moved in, which empties down a small waterfall into a ~15'X2'X1' stream that connects it to a larger ~25'x20'x3' pond with a small waterfall that empties into a crushed granite riffle area.

The water is circulated from the big pond to the small pond by this: Aquascape 91104 AquaForce PRO 4000-8000 Asynchronous Pump with Protective Cage for Ponds and Pondless Waterfalls, 7,793 GPH. I also have bubblers in both the top and bottom pond. I run the pumps year around.

Both ponds are stocked with a small local fish that that caught in the stream on the property, Russian River roach, which are minnow sized. They have been spawning and reproducing and appear plentiful, but I don't think the pond is overpopulated, though I did move about 10 fish back to the creek this summer. (The pond used to attract a lot of spawning chorus frogs, but I think the fish scared them away, though according to my research Russian River roach are not supposed to each frog eggs, just algae and bugs. I suspect maybe that the frogs can smell the fish and so avoid the pond. They are still very plentiful on the property and spawn in the vernal ponds in the pasture, where there are no fish.)

To control algae (and because I like plants) I planted fish weed and hornwort in both ponds, both of which are very plentiful. I also have: some native reeds in pots; a taro plant in pot, which has been sending out runners; and another type of potted plant which is native here but dormant in the winter and whose name I forget. In the stream, I planted native monkey flower this summer, which loves it, and in the beach of the large pond various grasses have taken root. Duckweed, which is locally pentiful, also appears on the ponds, but less so this last summer.

There is also a large oak tree over the large pond, which drops lots of leaves, the vast majority of which don't get cleaned off.

Until recently I was directing the backwash of the house's calcite filter into the pond, as a way to conserve water, but stopped doing so because of concerns that it was not helping the algae issue. Our well water is highly acidic and has lots of iron. We are also in rural semi-agricultural area and our somewhat shallow well produces water that has chloroform that we treat with UV. The system also has a softener, which backwashes well away from the pond. When we add water to the pond in the summer, it is with untreated water that bypasses the system.

There are quite a bit of a nutrients and algae in the area, generally; and puddles and vernal ponds on the property quickly get blooms

Issue

Over the last couple of years, I have had an evolving "problem" with excess algae. Earlier in the pond's life, during the summer, we would get large mats of algae that was yellowish green. That has diminished somewhat, though has not at all disappeared. What we are getting now though is a green algae that is not a the surface but rather appears to be through the entire water column and which is more plentifu in the winter.
(There is not very good picture of it attached). I don't want to treat the algae with chemicals and the plant load is already very high, at least as to the fish weed. Would love to get any thoughts or advice that you all have. Maybe create a filtration bog upland from the smaller pond? Change up my plant mix?

Cheers,

Stu


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[MitchM]

Hi Stu,
Could you please post some numerical water test results?
We can help you come up with a solution based on those numbers.
Also, I'm assuming Sonoma county is in California?

 

[stu]

Cheers, Mitch!

Yep, California. We are about 15 miles from the coast. Attached is a seasonal temperature range chart.

In terms of numbers, I got some somewhat surprising results. "L" = bigger and newer lower pond; "U" = smaller and older upper pond; "W" = untreated well water (some from a hose, so right from the spigot)

Ph: L-9; U-8; W-6.5
Ammonia: L-0 to 1; U-0; W-0
Nitrite: L-0; U-0; W-0
Phosophate: L-1 to 1.5; U-2; W-3 to 4

Re the Ph numbers, one possibility is that the calcite filter backwash resulted in a deposit of high Ph chemicals that have collected in the lower pond, and the upper pond's chemistry has also benefited more from the recent heavy rains. Also potentially relevant is that the algae bloom is much worse in the lower pond than the upper.

 

[MitchM]

It sounds like the iron and phosphate are fueling the algae plus you mentioned "chloroform", but I think you meant "coliform" bacteria.
I would test your water for nitrates.
My understanding of calcite filters is that they use calcium carbonate, which is only soluble to a ph of about 7. You mentioned other high ph chemicals, so if there are other chemicals used in the filter, please list them.
Take 2 ph readings, one first thing in the morning, one in the evening after a sunny day and post them here.
Also test your water for KH and GH in addition to the nitrates. API makes affordable test kits for those.

 

[mgmine]

You are on well water and in an agricultural area that says it all. You're fighting a losing battle just as I am. Save yourself a lot of aggravation and get a good UV light. That is the only guaranteed way to stop algae. Within a week you'll have clear water. It won't kill the string algae but will kill the blooms.