- Joined
- Aug 10, 2017
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- 48
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- Location
- Daytona Beach, FL
- Hardiness Zone
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After a year of using treated tap water to fill and top off my two connected 600 gal koi ponds, I switched to a rainwater collection system that currently stores 300 gals for topping off. During summer droughts, my pond loses up to 1-2% per day of its volume to evaporation and so my system can sustain about a month of no rain before I have to resort to tap water. I thought this would be a win-win until I discovered that my pond pH apparently was significantly affected by the change.
I don't normally test my water frequently, instead using observation (fish appetite, behavior, algae growth, etc) to determine if there is a problem. Under the new system I noticed that string algae seemed to be thriving this year where it had not shown up at all previously. Testing the pH I found it to be quite alkaline - nearly 8.6 - and although the fish seemed fine, my water plants (mostly lettuce, Alisma plantago, hydrilla and lilies) became coated in matted algae. There were no measurable nitrates or phosphates in the water. The water lettuce root systems became so infiltrated with algae that the perimeter of the leafy bodies was turning brown and dying. I used barley bales and physical removal to try and control the algae but eventually had to resort to propylene glycol-based algaecide treatments to halt the infestation. My fish (8 comets, 8 koi, all less than 6") continued to show good appetite and energy throughout the treatments. Even the snails endured them. Although my water was fairly clear of diatomic algae I added several dozen rock snails and four plecos to help my comets and koi try to catch up on the growth coating the pond tiles. I pulled out a dozen of the least-sick water lettuce plants and quarantined them in a tank with tap water six weeks ago.
Over the last two months the pond pH has acidified to about 7.6. The string algae situation seems to be stable, although the waterfalls and pond sides are still green. I can easily see down to the bottom (28") but the water looks tinted.
What is interesting is that the quarantined water lettuce have nearly completely recovered - their root systems are clean and perimeter leaves are once again a rich green and there is very little, if any, browning of leaves. I tested the pH in the tapwater-only quarantine tank and it is only 7.2.
I think that's what my tapwater-only pond pHs were a year ago - in the 7.2 range - when I had no problem at all with matted algae infestation - and when barley bales alone cleared any green tint in the water.
What's also of interest is that the pH of rainwater in urban areas should tend to be more acidic than neutral due to sulfates and nitrates in the atmosphere from automobile and industrial pollution. So why is my rainwater alkaline? Thoughts?
I don't normally test my water frequently, instead using observation (fish appetite, behavior, algae growth, etc) to determine if there is a problem. Under the new system I noticed that string algae seemed to be thriving this year where it had not shown up at all previously. Testing the pH I found it to be quite alkaline - nearly 8.6 - and although the fish seemed fine, my water plants (mostly lettuce, Alisma plantago, hydrilla and lilies) became coated in matted algae. There were no measurable nitrates or phosphates in the water. The water lettuce root systems became so infiltrated with algae that the perimeter of the leafy bodies was turning brown and dying. I used barley bales and physical removal to try and control the algae but eventually had to resort to propylene glycol-based algaecide treatments to halt the infestation. My fish (8 comets, 8 koi, all less than 6") continued to show good appetite and energy throughout the treatments. Even the snails endured them. Although my water was fairly clear of diatomic algae I added several dozen rock snails and four plecos to help my comets and koi try to catch up on the growth coating the pond tiles. I pulled out a dozen of the least-sick water lettuce plants and quarantined them in a tank with tap water six weeks ago.
Over the last two months the pond pH has acidified to about 7.6. The string algae situation seems to be stable, although the waterfalls and pond sides are still green. I can easily see down to the bottom (28") but the water looks tinted.
What is interesting is that the quarantined water lettuce have nearly completely recovered - their root systems are clean and perimeter leaves are once again a rich green and there is very little, if any, browning of leaves. I tested the pH in the tapwater-only quarantine tank and it is only 7.2.
I think that's what my tapwater-only pond pHs were a year ago - in the 7.2 range - when I had no problem at all with matted algae infestation - and when barley bales alone cleared any green tint in the water.
What's also of interest is that the pH of rainwater in urban areas should tend to be more acidic than neutral due to sulfates and nitrates in the atmosphere from automobile and industrial pollution. So why is my rainwater alkaline? Thoughts?
