Hi Mike. I googled phosphate levels for you and most of the literature says at 1.0 mg/l you will get algae growth also with a high ph. Frequent water changes are supposed to help this. Having said that my ph was high today after a water change--8.8 normally is about 8.4 and I have alot of suspended algae however with our cold spring this year I also don't have the plant cover that I should have on a pond that's in full sun all day. Don't have a phosphate test so not sure what the levels are. If you search this forum David wrote something about using stump remover to help plants use up phosphates in the pond.

You say you only have 2 fish in your pond--are they koi???
Also is does your pond have lots of plants?

The hydrogen sulfide smell could be from anerobic bacteria left in the pipe that is sitting. Is there some way you can flush those pipes in between use without it going into the pond. If the smell comes from the pond it could mean old sludge at the bottom of your pond and a lack of oxygen in the bottom of the pond. In my reading one recommendation was to lower an air stone to a level where you don't get the smell, run it for at least 5 days, then lower it another foot, run again--lowering air stone gradually to the bottom of the pond.

Horton wrote about stirring up sludge/dead plants etc on the bottom of the pond when cleaning can cause this smell and that stirring that sludge up can be dangerous to your fish. If you didn't clean your pond in the spring this might be the smell although from what you're describing sounds like more from the pipes.

Trying to figure out what to add/not add/change can be challenging!

As long as your pH is stable at 9.0, I would not do anything to try to lower it. A stable pH, even if it is on the high end of what koi prefer, is much better than a pH that keeps fluctuating. So is 9 normal for your pond? What is your kH reading? One thing I will caution you on though, is keep a very close eye on your ammonia levels, since ammonia is much more toxic at a higher pH.

Phosphate is harder to fix. I don't like chemicals, so I can't recomment the phosphate removers. I have friend in florida who has a similar problem.....very high phosphate right out of the tap. Her solution is water hycinth. She has a large pre-filter tank where the water flows through before returning to the pond. She keeps hundred of water hyacinths there and they remove the phosphates naturally. That might be a good solution for you.

Mike... I don't have answers to any of your questions, just want to say I'm glad to see you posting again. You have a lovely pond.
Anne

Hi Mike,

I agree the sulfer smell is most likely from the dormant pipe. I get that same smell when I flush the BD pipe. The way I have succesfully dealt with my high phosphate levels is Watercress. I have source water high in phosphates so I had to reduce the uneccesary water changes as well. My pond is over 5K plus SC and Filters and I have roughly 60 square feet of watercress. I have seen the bottom of my 4 foot pond all season. It is an amazing plant would do nicely in your zone. I have placed mine on floating planters wich turned in to watercress matts.

Regards,
Lisa

Thank you for the good help and support. The situation is under control for the time being. I did a major-major water change, forgetting about temperature shock and basically just kept testing the water.

I believe that the combination of relatively shallow water, a heat wave and the design of my pond are key. Some may recall I built a pond that was a "monument" to my background with stones and water, a pond and two streams with lots of falls and turning the water over about seven times an hour. My mantra was no fish, no plants, thus no particular filtration, etc. Lots of aeration. This was my pond until one day DW showed up with a bucket of fish and another of water lilies. So we ended up with a handsome comet and a lovely shubunkin. I enjoyed them almost right away and accepted the responsibility for their well-being (especially because they don't reproduce!). I always monitored water quality, did what I could to make a healthy home.

It all changed this early summer. I have a leak that takes away a lot of water. By a process of elimination I discovered it is one stream or the pipe feeding it. The ground seems dry so I doubt it is the pipe but in stream curves where there is lots of water motion. I turned the water down all around with a good look to the falls but vastly reduced volume.

My local pond place person recommended adding beneficial bacteria to break down whatever is on the bottom but I was leery of the advice. As I tested I noted that the higer readings were coming down. The water was really warm to the touch. So I cranked up the streams and the water cooled and the test results became perfect again. So I guess with how I am set up, no bottom drain, no bio-filter, just a skimmer with two pads and brushes and a good-size filter pond I am dependent on keeping a good flow to maintain the health of the pond. I guess this is an odd situation but I got what I got.

So off to repair the stream banks. There is nothing wet along the stream so I can only hope this is the right choice as digging up the pipe is not a choice!

A long post, sorry, I just needed to sort of "think aloud" and let you all know how it is going.

Thanks - Mike