Algae in Koi ponds

Koi keeping presents its challenges and quirks as we all know. And it seems as if it has been years since we took our first baby steps into this amazing hobby. When we look back it hasn’t been that long, yet the time had flown by so fast it feels as if we have done nothing else!

Perhaps you are just starting out, or perhaps you are a seasoned Koi keeping veteran. But whatever you are, the one thing all we Koi keepers need is information and lots of it about our hobby – and sharing as much of that as we can does the hobby much good. So don’t be stingy– share what has worked for you and what hasn’t with your friends and associates in thehobby. There are many of us who have made mistakes and lived with them, and then promptly made the same mistake again!

Today’s topic is algae and why we like it so much.

Algae is a plant. It puts oxygen into the water during the day and takes it out again at night. Green water is caused by really small algae – teeny tiny nanometer sized single celled plants. It replicates with lightning speed causing ponds to go slightly off colour – often a light grey, before becoming a light browny green and then suddenly, completely green – almost overnight.

Bazillions of the little wee planties in the water tend to prevent us from seeing our fish. Our fish don’t really care – Koi are carp and they are very comfortable in green murky water – just like the natural river and dam systems that are their normal living environments. The only cause of concern with green water is oxygen levels overnight and that fact that if something is going wrong with your Koi you won’t see it.

By and large green water is healthy water for your Koi. But we don’t really care – we like to see our Koi. Hence we nuke these algae cells with our UV lights – and remember that even if a UV is glowing purple it does not mean that the globe is still emitting sufficient UV to kill off the algae cells. You should replace the lamp/globe/tube thingy once every 8 to 12 months – so if your water is going green and your UV is ‘working’ – change the globe!

Then of course you get that blanket weed stuff. An utter nightmare as it grows upto a meter day and sloughs off clogging filters, pumps and generally becoming a bit of a nuisance. No UV is going to help you with this monstrous pond invader and so the only solution is to don the old bathing costume and jump into the pond with a good wire brush and scrape it off the sides.

Then let it go through your bottom drain and catch it all from your settlement chamber before it gets into the filters – or else you will have to clean those as well. The great thing about cleaning your pond of blanket weed this way is that you get to repeat the performance every few days until the blanket weed realises the superior will and determination that you have dedicated to the single minded purpose of its eradication. Once the message
sinks in the blanket weed will turn tail and run. Congratulations!

Or you could chuck in some Viresco, watch the nitrates hit zero and then watch the Koi go bananas for food and start to eat all the blanket weed just as it in turn is being starved for food. Or else you can just chuck in a bottle of Pond Clear and chemically nuke the stuff into oblivion (it is fish and other plant safe). The choice, dear reader, is entirely your own!