Swim Pond - string algae after spring run off

[Anon_GM]

Looks like 0.25 mg/L phosphate in the pond and about 1mg/L in the city water. I guess a water change out is not going to help lower phosphate content...

 

[IPA]

The algae is up taking some of the phosphates as nutrients. If you look at many managed ponds they use a method to skim the surface which would be an easier way to remove the string algae. Normal pond Skimmers I don’t think would work for you though, too small and need to clean too often. Near where I live there are run-off ponds along interstate on and off ramps. They use huge collectors in the center to skim but I’m not really clear on how the system works as a whole.

 

[Anon_GM]

I read somewhere that geotextile on top of the drainage pipe under the gravel can clog and cause a lack of flow through the bog. I noticed that the only area of our pond that does not have geotextile over the agg pipe is clear of algae vs. the other areas where the geotextile over the agg pipe appears completely clogged with fine silt. Do I need to dig up the agg pipe and remove the geotextile that is blocking the flow?

 

[Jhn]

I read somewhere that geotextile on top of the drainage pipe under the gravel can clog and cause a lack of flow through the bog. I noticed that the only area of our pond that does not have geotextile over the agg pipe is clear of algae vs. the other areas where the geotextile over the agg pipe appears completely clogged with fine silt. Do I need to dig up the agg pipe and remove the geotextile that is blocking the flow?

Without a doubt, geotextile fabric will clog. That is what it is designed to do....catch sediment. If it is inhibiting the flow of water through the bog then yes I would remove it.

 

[TheFishGuy]

First year (2018) - late summer warm water (filled with city water) little to no string algae (could be easily controlled with manual removal)

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I have attached some pictures of the pond below. We built our pond summer 2018 iand we didn’t have any algae problems the first year even in the warm weather. The pond was filled with approx 70,000L of city water.

In the fall of 2018 and then in the subsequent spring we had a substantial leaf drop and soil runoff into the pond. I believe this is the major factor that has resulted in large algae issues since then, though we continue to have excellent water clarity. We have adjusted the drainage and removed the tree responsible for the leaf drop so we do not have these issues going forward. t

Since summer 2019 we had a large string algae problem. We didn’t think about changing out the water until this year. A couple weeks ago we changed out 50% of the water in the pond. Just draining the pond and vacuuming the biomass out of the bottom and route and changing the water killed the algae back for a week or two but it is back with a vengeance. We’ve never had any issues with water clarity or pea soup algae only The string algae at the bottom and around the plants.

We’re trying to get some lilies established but we didn’t realize for the first two years that they need to be potted and won’t grow alone in the gravel. We are considering retrofitting a skimmer and a water feature to filter the water additionally.

Design: The water is circulated under gravel by four bubble pumps pulling water through pipes under the bog area and aerating the water. There is no additional filtration system.

My question: since the issue seems to have been caused by nutrient run off and leaf drop will a 100% water change out solve the issues (we had no algae in the first year)?

Water quality - unknown (do not have a kit)
* Ammonia Level (pond)
* Nitrite Level (pond)
* Ammonia Level (tap water)
* Nitrite Level (tap water)
* Ph Level, pond (If possible, KH, GH and chlorine)
* Ph Level, tap water (If possible, KH, GH and chlorine)
* Brand of test-kit used and whether strips or drops?

Other useful information:
* Water temperature? - very warm in shallow zone (12" deep) usually a couple degrees below day time high
* Pond size and how long has it been running? 45'x35' with 12'x24' 6.5' deep zone; approx 70,000L
* What is the name and size of the filter(s)? bog only
* How often do you change the water and how much? did one 50% water change this spring
* How many days ago was the last water change and how much did you change? 1 month; 50%
* How many fish in the pond and their type? no fish; lots of frogs, bugs etc. wildlife also visit occasionally
* What kind of water additives or conditioners have you used? hydrogen peroxide (1L @ 3%/1,000- L)
* What do you feed your fish and how often? n/a
* Any new fish added to the pond recently? n/a
* Any medications added to the pond? n/a
* List entire medication/treatment history for fish and pond n/a
* Any unusual findings on the fish? n/a
* Any unusual behaviour like staying at the bottom, not eating, etc.? n/a

First spring (2019). Many plants did not survive the winter freeze. Also we did not understand the importance of potting/fertilizing plants. We had significant leaf drop in fall 2018 and spring run off from ground into pond in spring 2019. The tree has now been removed and drainage improved so we did not have these issues in spring 2020. I vacuumed out the leaves and silt (run off) in spring 2019.

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Late summer 2019. Warm water at this point was contributing to massive string algae. We tried to increase our plants (harvested from local water ways). We still were not potting/fertilizing. It was a losing battle...

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Algae was choking out everything.
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and clinging to the walls
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some visitors in fall 2019 (you can see heavy string algae even with the cooler water)
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Spring 2020 crystal clear and COLD water before plants came up
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String algae was back with a vengance once the water started to warm up in may. We have added many additional plants and many potted lillies since the photo was taken.
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I swear I saw this pond on a website that was like " top 10 creative swimpond ideas"