High pH and phosphate in my pond

[Dror]

Hi all

We have an approx 3000 gal pond, with a waterfall that runs continuously, so I believe it is well aerated. It is well established (approx 10 yrs old). It is reasonably well planted, with 2 water lilies, and irises and other plants around the edge. At the moment, we have about 12 assorted goldfish, between 6 & 10" long. In general, we have never had a major die off, but we seem to lose a fish every week or two (unfortunately, Im not enough of an expert to recognize any obvious symptoms), so I am worried that something about the pond conditions is not right. I began testing the water recently and I notice that the the pH is consistently high - about 8.5 in the mornings and rising to 9 in the evening. The KH is about 220 ppm and GH about 130 ppm. Ammonium and nitrate levels are 0, but phosphate levels are about 2 ppm. We have never had a problem with green water, but constantly have green algae growing on the stones and rocks in the pond. We try to keep the pond clean of debris and it gets an approx 10% water change every week or two during the spring - fall.
I have read in various places online that a pH greater than 8.5 can be harmful to the fish, so I tried lowering it with PondCare pH down adjuster. However, 3 treatments with this, at the recommended rate, had no effect. I suppose this is because of the high KH. I am uneasy about continuing to add more chemicals to try to reduce the pH. I have also read that provided the pH is stable it isnt too much of a problem, so Im really not sure how much I should worry about the pH
My questions for the experts out there are whether they think the pH level in the pond is a problem, and if so what can I do to correct it, considering the hardness of the water. The hardness comes from our water supply, but the pH of our water supply is about 7, so it seems to be increasing in the pond.
Second, how much of a problem is the phosphate level, and what should I do, if anything, to deal with it. Could one or other (or both) of these parameters be contributing to our periodic fish loss, or is something else going on?

Thanks in advance for any advice

 

[TheFishGuy]

I am not the guy to look at for water parameters, but will say that the water change at your rate of stocking is unnecessary, any depending on your source water that could be the reason for high ph. I would be in favor of stopping with the water changes, and seeing how things stabilize out.

you are very right that chemicals aren't always the answer, and others will help you out with what types of chemicals may be good or bad in your application.

 

[JamieB]

The ph is better if it’s stable, and a slow change. I’ve got high ph here, low 8s from the source, so if you think it’s a problem in the pond, you want to look into slowly introducing something to acidify the water. I’m no expert, my first thought is peat moss but that would break down into nitrite nitrate, etc. So instead, wait for experts to chime in. However I will ask if you are quarantining your fish before adding them in. It’s possible some pathogen or parasite was introduced. Post pics of the next one you loose, look it over for discoloration along the gills, tail, fins, etc, wounds, sores. It could be a predator, illness, or something else like that.

 

[WaterGardener]

Your pH is not a problem. PH needs to be stable and anywhere between 7 and 10 is fine as
long as it doesn't jump around

As you have found, trying to lower it will only make it fluctuate, stressing the fish.

 

[j.w]

@Dror

 

[Dror]

Thanks all for the input so far. I will post pics the next time we lose a fish.

Any thoughts of the phosphate levels we're seeing? Is that a problem we should worry about, and if so, what to do?

 

[JamieB]

Is the source water the source of phosphate or is it something in the pond? Post a picture of the pond, tell us how it was made, what kind of rock you may have in it, etc. I’m wondering if you’ve got rock that’s increasing the ph in the pond, think limestone, and or rock that’s been treated with a phosphate that’s leaking out into the water.

 

[Dror]

Here are a couple of pics. Im not enough of a geologist to know what kinds of rocks weve got. I do know that the pond is fully lined.
You mentioned the source water so I tested that as well. That may be part of the problem - looks like the phosphate levels there are about 1 ppm.

 

[GBBUDD]

any algae blom where you can see the shape and colors of your rocks is definitely not the problem . it is a sign of a healthy pond. Lack of algae however can mean two things one lack of nutrients. or possibly something in the water like phos[hates to deter bacterial growth. which leads me to the first question do you have well water or city ?

 

[Dror]

We're on a community well system. And yes, when I tested our source water in response to JamieB's earlier question, I can see phosphate levels of about 1 ppm. I don't know if that completely explains the phosphate levels I measured in the pond, which were about 2 ppm. But, either way, are these levels something I should worry about, and if so, are there any recommendations for dealing with them?

 

[GBBUDD]

Alot of chemicals don't or they evaporate slowly. So your 1 part in a storage area "the pond " can certainly accumulate thats where bogs thrive over mechanical man made filters . Mother nature is plants absorb this as food within the roots.

 

[JamieB]

You can relax, you just need plants. When you add water to the pond, it’s already at 1ppm, then some water evaporates, fish do what they got to do, so you add more water, and then it tested at 2. A simple solution is to get more plants, and set up a way to move your water. This will ensure that the pond is getting circulation, and that lets plants pull the waste from it easily. The more plants, the better. If possible, set up planters that are designed for submersion on the tall rocks, fill with pea gravel and plants, there are long threads about what plants to use, and how to plant them. Then give it time, you’ll see the numbers coming down eventually, instead of slowly climbing.

 

[Dror]

Thanks for the input. The pond is already planted - see the pics up. And we have pretty good circulation. Its actually in effect a 2 pond system, with a stream and small waterfall between the 2. The upper pic above shows the small shallow upper pond. This is not planted. The bottom pic shows the much larger lower main pond - this is where the fish are. Do we still need more plants?

 

[brokensword]

Thanks for the input. The pond is already planted - see the pics up. And we have pretty good circulation. Its actually in effect a 2 pond system, with a stream and small waterfall between the 2. The upper pic above shows the small shallow upper pond. This is not planted. The bottom pic shows the much larger lower main pond - this is where the fish are. Do we still need more plants?

water lilies aren't the best for filtering the water colum; for that, the floaters (water lettuce, water hyacinth) work best. Aim for 60% coverage to help keep algae blooms down. Both will reproduce very quickly so you don't need to start out with many. I usually start with 2-4 and by mid summer, am thinning them out. But the sooner you have a herd of these, the sooner your water will clear.

 

[GBBUDD]

your pond appears pretty healthy . Don't confuse peach fuzz on the rocks as a bad thing. The answer to needing m I re plants depends how ones pond is doing. And your appears to be doing very well. I belive you had said you lost a fish maybe there's more going on then meets the eye. With ponds the less you do can often be the best you can do for tge pond. I'm not talking no maintenance like leaving k eaves that fall in tge pond but more let the pond do its thing and see if it can balance out in time