High pH

[CharlotteSC]

Here I go again with another year of floating pond scum algae. Life has been busy but I hate to tear down my pond. I have 1000 gallons in almost full sun with about 6 small goldflish that have not been fed in 2-3 years. Every spring I vacuum out the muck with my pond vac. This year I added some of the bacterial booster stuff in the spring.

No runoff into the pond, water lilies and marginals only minimal fertilzer with pond tabs. EPDM liner, no reactive stones in water. Skimmer with 9.5 pondmag pump leads to a canister filter/uv with those sponges inside and then to a filto falls with bioballs and back to pond.

I can't do anything about the sun but my plants just don't do as well as they did several years ago. I'm not sure why. I am afraid of adding more fertilizer.

Our water GH out of the tap is about 0 for GH and very low KH. Last year, I used the ice melt product to slowly raise GH some and baking soda for Kh with I have to keep adding with new water or rain.

So here is my problem, the water is clear but the scum makes it ugly every sunny day. The only water parameter (other than struggling with hardness) that is out of whack is the ph which remains high - no matter what I do. It is always above 8.5 - 9.00.

Would this ph cause my plants to do poorly? Water Hyacinth will not live in the pond. I don't normally like to use chemicals but we are at the point of tearing it down if we can't fix it.

 

[Lisak1]

High pH COULD affect some plants, but I don't think it would bother all plants. Maybe research a bit to see which ones like the higher range.

We were in the 9 plus range the first year or so, but slowly - while changing nothing other than allowing time to go by - the pH came down to a more reasonable range. I stopped testing at some point, so I don't remember the specifics, but things did slowly settle in.

Are the plants (other than the lilies) in pots or planted directly in the pond?

 

[CharlotteSC]

Yea, I've had this little water garden for more than 12 years but it seems in the last 2 or 3 things have really gone to pot. I even did a 50% water change last year but it didn't help. I'm sure I'm missing something. My plants are all in pots. This was my first pond and I did dumb things like not have shelves for pots except for on one side - that's where the marginals are

 

[WaterGardener]

Can you put some shade sails over the pond? You might have to put some posts up to tie them to, but they work well for shade.

 

[Mgessert]

Sometimes items in the water like certain kinds of rock (limestone), coral, oyster shell, or cement, can raise the pH.

 

[CharlotteSC]

Can you put some shade sails over the pond? You might have to put some posts up to tie them to, but they work well for shade.

Good idea but not really an option. I just wish I could get my lilies to grow lol

 

[CharlotteSC]

Sometimes items in the water like certain kinds of rock (limestone), coral, oyster shell, or cement, can raise the pH.

Oh my gosh, you might have something there. I do have oyster shells in the pond to try to raise the hardness.

 

[cas]

Our water GH out of the tap is about 0 for GH and very low KH.

Did you test your pond water?
GH is the calcium and magnesium required for fish bone and scale development, and trace elements such as iron and phosphorous that are needed for plant growth. GH also bolsters Alkalinity which in turn buffers the pH, preventing any wide pH swings.

‘Higher’ plants have far more complex needs. The assumption that the fish waste (ammonia) will supply all the required nutrients is not true. At some point the plants will slow or even stop growing due to a deficiency in one of the other required nutrients. Fish poop provides nitrogen and phosphorus, and a few other trace elements but it contains no potassium, no usable iron or magnesium and very little sulfur or calcium. These all need to be added or the higher plants (plants other than algae) won’t thrive. If the plants are yellowing, they may need more iron.

 

[Mgessert]

What an interesting topic! I found this article about the cycle of pH in ponds. I didn’t know it was so complicated. “Managing High pH in Freshwater Ponds”

Managing high pH in freshwater ponds

This factsheet by the Southern Regional Aquaculture Center (SRAC) gives information on managing high pH in freshwater ponds.

thefishsite.com

 

[Rashad]

Charlotte, I haven't tested the ph in a while but here in New Mexico we have really alkaline soil and water, and our pond PH was around 8-8.5 last I checked. For me the trick has been to find plants that do well in more alkaline environments. Yerba Mansa has done amazing, water cress tolerates it pretty well, irises are holding up pretty well. The goldfish are doing fine. Water hyacinth also didn't work for me. Lilies have been doing well and provide shade to reduce algae. Green onions have worked well as a marginal plant. Just buy some from the store and plop them in the gravel somewhere.

 

[CharlotteSC]

What causes plants to not do well? Other than specific preferences - I'm beginning to wonder if my hesitancy to fertilize the lilies (only using a couple of pond tabs in Spring) in an effort to keep organics out of the water is adding to the problem?

 

[CharlotteSC]

About 6-8 hours of sun per day.

 

[CharlotteSC]

Did you test your pond water?
GH is the calcium and magnesium required for fish bone and scale development, and trace elements such as iron and phosphorous that are needed for plant growth. GH also bolsters Alkalinity which in turn buffers the pH, preventing any wide pH swings.

‘Higher’ plants have far more complex needs. The assumption that the fish waste (ammonia) will supply all the required nutrients is not true. At some point the plants will slow or even stop growing due to a deficiency in one of the other required nutrients. Fish poop provides nitrogen and phosphorus, and a few other trace elements but it contains no potassium, no usable iron or magnesium and very little sulfur or calcium. These all need to be added or the higher plants (plants other than algae) won’t thrive. If the plants are yellowing, they may need more iron.

I have pond tabs... I have been afraid to fertilize much due to the concern about adding more nutrients to the water.

 

[Criscar]

Have you ever tried adding floating plants rather than only having the rooted ones? They can do a great job of mopping up excess nutrients in the water column and shading the pond to keep down algae growth. My pond is usually in the low 8s for Ph and hornwort does fine with that ph, for example.

 

[Mgessert]

There are supplements you can add that don’t have nitrogen, like Maxicrop seaweed powder, dtpa chelated iron, and magnesium sulfate (epsom salts). If it were me though, I’d also provide some shade over half of it until the scum clears up, either plants or a structure.