My tank is green. Why?

[Americancichlidsaredabest]

Hello everybody I have a 20 gallon tank with 3 danios 6 mollies 4 rio von flame tetras and 3 corydoras

all the fish are eating just fine and are doing well. I have a sponge Filter and a HOB. It clears up when I do water changes which is about 50%weekly then over the next few days it turns green. Any ideas why that is?

 

[kno4te]

Hard to say. Would look at tank location. Maybe some extra light from a window?! Light on time is long? Test ur water recently? Or more waste that the algae is using as a food. Or a combo of what I mentioned.

 

[Americancichlidsaredabest]

I made sure to check the tank isn’t in any direct sunlight and I don’t run the lights a lot. I’ll check my water parameters right now

 

[Jexnell]

Sounds like an algea bloom. Does the tank receive a good amount of natural sunlight from a nearby window. And or are the lights on for a majority of the day. Are there no plants in the tank to out compet the algea for the nutrients in the water column?
If it's the sun you can move tank, darken the sides the sun is coming in thru. Provide shade via curtains of blinds etc to control the amout of sunlight getting to the tank.
If it's the light you can lessen the hours it's on or turn it off altogether and only use it when actually viewing the fish.
If you don't want to deal with aquatic plants you can use several types of house plants instead, submerge roots only and will consume the nutrients instead of letting the algea grow unchecked.

 

[Americancichlidsaredabest]

I just checked my water parameters
Ph=7.2
Ammonia=0
Nitrite=0
Nitrate=5 ppm

also as I said before tank is in no direct sunlight and I only use lights when I watch and feed my fish. I don’t have any live plants as I need a thicker layer of gravel to do so which I will be getting soon.

 

[Americancichlidsaredabest]

Also I don’t really have any experiacnce in keeping plants. What do I need to keep them and what are some easy plants to keep

 

[Hybridfish7]

Amazon swords, hornwort, vallisneria, subwassertang or java moss, you'll have to see what does better in your water. Crypts are also easy. Anubias and java ferns are easy to keep alive, but kinda slow growing.

 

[tlindsey]

Anubius and Java Fern don't require gravel or substrate but need to be secured on wood, suction cup clips, or special little plant baskets.

 

[Trouser Cough]

Place a UV Sterilizer inline on the return side of your HOB. Whatever's causing the algae bloom will still be there but the algae itself won't survive a trip or three through the sterilizer.

 

[Disturbed.)]

While I agree plants are the natural and more aesthetic approach they will further complicate your algae problem. Your water is turning green because of light and nutrients in the tank. Adding plants will mean you will need to keep those tables in check to feed the plants and starve the algea. It's something most aquarium keepers eventually do because it adds to the challenge.
It seems like you are just getting started so I'd suggest a small UV sterilizer. Learn plants on your own terms not when your fish tank has a problem you are trying to fix. That way you get better at keeping your parameters in check in a fish only tank. Go get a 9w internal uv like the green killing machine or whatever brand / price you want. All of the submersible units are cheap crap and wont do much to help your fish but they will clear your water. Run it the next week or 3 while you are adjusting your feeding and water changes then clean it and pack it away until you have the next GWA outbreak.