Hello First Post
I have had my pond for two years now. This winter I lost all of my Koi (16). Most of the fish died after the ice had melted , over the last couple of weeks. The pond never completely froze over, as I used an aerator to keep the pond open. I covered the pond with a net to ensure that all the dead leaf matter etc. was kept out of the pond in the fall. The only thing I can see that may have cause the problem was leaving the hogwart in the pond over the winter. This was done on advise that I received from the internet. I was told that the hogwart would overwinter and survive the cold. Made a lot of sense if you think in terms of the hogwart producing oxygen. However, in looking at the hogwart, after the ice had melted, it would appear that most of it die over the winter. This could be my problem as far as the fish dying. What is your opinion? The only small doubt I have is the majority of fish survived the winter and have died since the ice has melted.
All that said, the main problem I have is string algae. This started last summer and seemed to have survive the winter. Everything in the pond, liner, rocks and plants are covered with the algae. It is my understanding that once the string algae is established it is extremely difficult to eliminate. Last summer I tried everything to control the problem. I do not have excessive fish, my surface is well over 60-70% covered by floating plants, I had amble oxygenating plants, I used concentrated barley treatment every couple of weeks and an organic water treatment to enhance the balance of the pond. My thought is to get rid of the string algae and start fresh.
My question is would it be better to treat the existing water with an algaecide and try and kill all the string algae, after removing my other plants (which also are coated with algae) or drain the pond in an attempt to scrub off the liner and rocks?
Thanks in advance.
Welcome to the forum! I just answered the same question that you e-mailed to me. Here was my response.
I'm so sorry. How big were your koi? How big is your pond?
I think you mean hornwort. I've had times when it overwintered and other times when it died. Too much rotting material can deplete oxygen and raise decomposition gases (hydrogen sulfide and methane which can be toxic in high doses). I can't say how much impact the hornwort had on the gas levels. It is strange that the fish died after the ice all melted. Did you test the pH, ammonia, hardness, and/or oxygen levels? I would start with those. At the time that the fish died, were you running the filtration system? What about aeration? I know you said you aerated to keep a hole in the ice.
Hair algae is not always a problem. If it traps animals, clogs filters, or strangles plants, then yes it's a pain. Otherwise, like other plants, it is filtering the water and adding oxygen during the day. The UV sterilizer will kill suspended algae which provides more nutrition for the attached algae like hair algae. It sounds like you had enough plants though that should have competed with the algae. Newer ponds are more prone to algae so I wouldn't worry too much about it. I had some hair algae and don't worry about it. It comes and goes. You might want to test your pond's nitrate and phosphate levels. Those feed the algae. Of course, if the algae is growing well, you shouldn't read any nitrate or phosphate!
I never think algaecide is a good choice in a natural pond. All algaecides are toxic chemicals. Even if they were magically safe chemically, when all that algae dies, it causes a massive drop in the oxygen levels and pH fluctuations. Since it would mean killing a large part of the natural filtration in the pond, afterwards, all kinds of algae would proliferate even more greatly leading most ponders to then add more poison to kill it yet again. Fish kills are common when algaecides are used. Scrubbing algae is futile.
I prefer the natural route - add plants, shade, good filtration, good aeration, barley, more plants, and time.
My page at http://www.fishpondinfo.com/plants/algae2.htm has even more ideas.