Over Wintering And Algae

Pond plants, algae, etc.

Over Wintering And Algae

Joined: 11 Apr 2011, 13:32

11 Apr 2011, 14:12 #1

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.


Fishy Brainiac
Fishy Brainiac
Joined: 01 Sep 2003, 21:10

11 Apr 2011, 23:51 #2

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.

Good luck!
Robyn, Analytical Chemist, Zone 6/7, Maryland
Servant to 4 cats, 1 rabbit, 3 guinea pigs, 2 dwarf hamsters, 1 redbellied turtle, 3 freshwater aquariums (65, 50, & 20 gallons), 2 saltwater aquariums (6 and 12 gallon nano cube reefs), 7 outdoor ponds (1800, 153, 50, 30, 20, 20, & 12 gallons), 1 indoor pond (20 or 50 gallons, winter only), crickets, mealworms, and hundreds of fish (of about 18+ species), amphibians, snails, shrimp, corals, crabs, worms, and so on in those aquariums and ponds. A mostly full list of my current animals is at http://www.fishpondinfo.com/animals/animallist.htm

Fishiedude ribaward

Fishy Connoisseur
Fishy Connoisseur
Joined: 01 Nov 2008, 22:08

11 Apr 2011, 23:57 #3

Hi bwb518
We've all had problems with it but how many of us have had a close up look at exactly what Algae is.
Basically algae are single celled plants, they come in two differnt forms the first we'll look at makes or composes that we commenly know as hair algae though others know it as string Algae.
This form is the easiest of the two to control and there are various ways of getting it out the easiest way is to buy a special brush that is designed to capture the strands and by rotating the brush the algae is snagged and can thus be removed.
The second form however is when the single celled free floating algae blooms which many describe as a soup where your koi totally disapear.
During the day the algae bloom is the same as any other plant in that it makes Oxygen and consumes carbon dioxide but at night its a different matter as the bloom now goes into reverse consuming Oxygen and producing carbon dioxide which we all know bodes ill for our charges.
What else does algae do well for one like all plants it will consume nitrates which we dont really want in our ponds. Now Here comes that classic catch 22 moment it needs nitrates to grow thus becoming a bloom which we dont really want so what do you do , have high nitrates in the pond and green water or do regular maintenance water changes etc and keep algae down so good husbandry is an absulute must !!!.....
Well for one we dont really want either in our pond so regular tests need to be done if your going to keep it down.
If however you do end up with that classic pea souper of a pond there are ways both natural and chemical to remove it .
How do we set about removing the algea ?
Barley straw bales or barley straw extract, we can also use hydra-Cyrstal to remove green water these are the more natural ways of doing things and should we get it this is what we would use.
We wont go into them but there are many other products on the market NTLabs make one of the better ones, as do other well known companies but mostly however they are chemical, which we dont really want as mistakes can be made.
So as you can see its always best to research your chosen way of removing algae you dont want any nasty suprises whilst treating the pond for it do you
Natural is the best way forwards in our eyes here is a link to Hydra-crystal :-


I hope this helps
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