Always green water - could it be the light?

Hey folks, been battling with this 20 gallon tank for a year now and have tried about everything.

Basic tank with 7 ember tetras that are fed every other day. PH level is right around 6.8 and all other levels looks good. I have been doing 30% water changes every couple days when the green gets darker. This picture is after the latest water change which is about as clear as the tank gets. I have done 75% water changes at times and it always comes back to this same spot or worse within a week or two. I have been using API Algeafix every 3rd day.

Aquon LED light which came with the hood is only on 4 hours a day and the room is otherwise blacked out.

The only thing I can think of at this point is that the LED lights in the hood are so bright they trigger Algea, otherwise I am at a loss - any help is appreciated.

I am not sure that is green water, it almost looks like something else. Green water is caused by a reproduction of unicellular algae which feed on organics/nutrients and need light. Stronger light does encourage this if the organics are adequate. A whitish haze could be a bacterial bloom which is caused by the rapid reproduction of certain bacteria that feed on organics. Diatom blooms are similar. As are organic blooms [I battled this in one tank for two years].

Other possibles are the gravel slowly dissolving (I had this many years ago)--do you know the gravel make-up? Or one or both of the artificial decor...were these specifically said to be aquarium safe?

Don't use the Algeafix, it is detrimental to the fish, and as you have seen it isn't working here. Live plants, just some floating plants, might help (they would shade the light) if this is organically-related.

The organics cannot be high with so few small fish and minimal feedings, which is why I am wondering about the gravel and decor.

If it is green water, then it's caused by the light and no live plants in the tank.

Green water is simply a term used for an algae outbreak where numerous single celled algae multiply and become so dense the water turns green.

Algae grow anywhere there is water and light. In your tank there is light and nutrients but no live plants, so the algae grows instead of the plants. If you add some live plants to the aquarium, then the algae would not do as well and the water should not go green.

Some good plants to try include Ambulia, Hygrophila polysperma, H. ruba/ rubra, Elodia (during summer, but don't buy it in winter because it falls apart), Hydrilla, common Amazon sword plant, narrow Vallis, Water Sprite (Ceratopteris thalictroides/ cornuta).
The Water Sprite normally floats on the surface but can also be planted in the substrate. The other plants should be planted in the gravel.

Thank you for the responses. I get the point on live plants but also agree that there really shouldn’t be much for organic material in the tank. It’s been years but have had plenty of luck running tanks with no live plants and much more sunlight in the room. One interesting thing is on water changes I feel like there is always too much weird white material kicked up that just shouldn’t be there. Has me wondering if the gravel is falling apart now.

Here is a picture of the tank 3 days after water change

Update, I removed all the gravel and fake plants from the tank and completed two more water changes, when I removed the gravel there was a green cloud coming off the gravel as I removed it. Still can't tell what it exactly is but that variable is removed. The water seems almost stained yellow/green now. I will let it settled and filter while doing 20% water changes daily for the next couple days to see if it clears up. With little light and zero chance of waster sitting around if it is algae related it should clear in the next few days.

I had only plastic in my tanks for many years, it was easy to clean and maintain but live plants is the way to go. Just simple easy to care for floating plants like anacharis and wat sprite can improve your tanks water quality and add oxygen to the water.