Green water in my goldfish tank

Question
Hello, Chris!  After reading the types of questions you can answer, I related most to the section that said, "What's this stuff in my tank..."  

We have 4 gold fish in a 20 gallon aquarium, with 2 tiny little algae eaters.  We recently switched to an air filter system from the standard filter systems where you switch the cartridgers (as it constantly was still leaving algae all over the glass).  We began with one goldfish a year and a half ago, and have added a couple more, upgraded tank sizes, but in general we are very clueless to a lot of fish information!  I have heard how goldfish are the dirtiest, to do the 25% water changes weekly....and all this we do.

Now, once we set up the air filter system, it was PERFECT!  Water looked GREAT!  We could actually SEE our fish again!  But once I did the first water change, suddenly the water became green, then began getting even more green.  I did another water change and still the same.  Not sure why everything was going great with the new air filter system until that very first water change.

And I wouldnt even know how to do the nitrate/ph/amonia checks, so if this is something i must begin doing, that's no problem, just walk me through it!

Thank you VERY much, Chris! We look forward to hearing from you soon! Also, other than our little buddies swimming in green, they still appear happy and healthy and know definately when it's feeding time!


Answer
Hi Jamie;

If it's actually the water itself that's green and not just the glass, it's very difficult to get rid of and sometimes just has to run it's course and go away on it's own. Here are is a web page that will give you some suggestions on controlling it;

http://freshaquarium.about.com/cs/maintenance1/p/greenwater.htm

If the algae is growing on the inside walls of the tank, just wipe it off. Some green algae forms in all tanks somewhere and is actually a sign that it has a healthy biological system. It is a very natural thing and not necessarily a sign that it's "dirty" as is often believed. Wipe the algae from tank walls and surfaces and clean your decorations by removing them, scrub with an algae pad (no soap) and put them back in. Filtration is not meant to control the algae, just biologically process the fishes' waste. If the filter can't control the waste and the waste produces excess algae, one or a combination of situations exist; Overcrowding, overfeeding, inadequate filtration, sunlight, too small a tank.

When you say "air filter system", I am hoping you don't have an undergravel system. If there are plates under the gravel with tubes in the corners and air bubbles come up out of them, it will not work to keep goldfish waste under control. The gravel will become plugged with waste and it will collect under the plates eventually so that it will foul the water and they will get sick. Undergravel systems are meant to be used with smaller fish that have much less waste. Goldfish are very messy fish so 4 of them give quite a big waste load to a 20 gallon. Goldfish really need a minimum of ten gallons of water per fish because of their massive waste production and potential size of 6 to 8 inches. If you were to graduate to a 40 gallon that would be enough for now. They may need larger depending on how much they grow.


The kind of filter systems goldfish need are the "power filter" types that hang on the back and form a waterfall going into the tank, or even better are the types called "canister filters" that hook up with hoses outside the tank. They collect and process large wastes, unlike the undergravel systems. I usually recommend a filter rated for a tank a little larger than the one you keep your goldfish in. They just need it.

At Your Service;
Chris Robbins