Green/Blue Water... algae?

[islandboy]

I have a 55 gallon tank that I am using to house 4 Red Ear sliders. It has a Fluval 304 Canister Filter (foam, ceramic rings/prefilter media, car-ammo chips, fluval biomax), air stone, heater and a few rocks for the the turtle to get out of the water.

Had this setup for about a year now, no real big problems.

Within the past month I drained almost all the water out, rinsed off the rocks, changed filter media, only thing left in the tank was the gravel. After a week or so I noticed the water turning a blue/green color but no visible signs of algae. The tank is situated right in front of a window but the blinds are usually closed.

Any reasoning on why the water would be turning a bluish green color?

I haven't done any testing on the water yet but will do it tonight.

[RichBowyer]

You don't have any copper objects in there do you? I've seen copper do that. very pretty, not healthy.

[islandboy]

No copper objects that I am aware of.

I have gravel rocks on the bottom, bigger rocks which the turtles use to get out of the water and two aquarium decorations... no copper.

[Commodore 64]

Could it be Green Water Algae? ([Only Registered Users Can See Links.])

[carebear]

Sounds like you have algae bloom. Try less lighting, maybe 4 -5 hours in a day and possibly you're over feeding. Your tank isn't getting direct sunlight is it? This can speed up the growth of the free floating algae in the water. Good luck!

[Furface]

Most likely an algae bloom. Some way the water got a shot of nitrogen and/or phosphorus. Perhaps the water you added already contained the nutrients, you fed heavier, or disturbing the gravel helped old food decay with more oqygen available and released the nutrients. Just change out more of the water more often.