View Full Version : how to prevent green water?

03-21-2010, 02:13 PM
hey guys.
we set up a tiny above-ground plastic pond (about 15 gallons i'd estimate?) that we bought used at our club auction a few months ago. pond has a water pump turned into a sponge filter. here in florida temperatures are usually warm so originally didnt have a heater, then the cold snaps came 3 of our fish died, so now there's a 200w heater in there keeping the temp at about 80F.
i have sand and river rocks in the bottom, and several snails.

as of the last 2 months or so there's only been one medium sized mayan cichlid in there.

about 2 weeks ago i noticed we were getting green water. when looking at the pond it looked greenish, but the water coming out of the pump on top was clear. by yesterday it was pure green and the water coming out of the pump was green too:ssuprised:

the fish was alive and doing well, so i took him out and did a complete overhaul, removing all the water, scraping the sides, rinsing and removing all the water. now it looks almost clear again, but unless we do something to prevent it, i can only imagine it'll happen again.

on the sides of the pond only the front part was covered in green algae (came off really easily when cleaning). the back part of it, which is shaded by the base of the pump outflow, had no algae. so i'm confident the algae/green water came from the exposure to the sun. but how does one prevent that with an outside pond?

are there chemicals one is supposed to put in the pond to prevent green algae?


03-21-2010, 02:17 PM
The culprit in your algea situation is the sun. There are a few algea inhibitors and barley products that can help in your situation. Just go to a pond supply store.

03-21-2010, 04:16 PM
In a pond that size,especially above ground ,keeping green water from happening will be near impossible without a uv clarifier.Chems will only work short term and will build up to toxic level too quickly.Barley straw works a bit but only of the algae inducing issues aren't extreme [in your case it will be].Shading the pond so it only gets minimal sunlight will help alot.3 things I would do would be cover the whole pond with surface plants such as water lettuce or hyacinth,install an aeration pump,use barley extract solution.If these things don't work ,the only solution is a uv clarifier.