Half an algae problem

[Cinnebuns]

I'm confused here. 

This is a divided 10 gallon tank. Divider is a sponge. Side 1 has a lot of algae and side 2 has none. They share water and I have tested each side independently a couple of times and their parameters always come out identical. Nitrate being the one I would think might cause the difference in algae. Both sides get equal lighting. 

Here are the differences in the sides:

Side 1:  about 30 2 week old guppy fry, 2 ramshorn snails, aquarium coop small sized sponge filter, food tends to build up more on this side so I have been feeding less. 

Side 2:  about 10 6 week old male guppy fry. No snails (that I can see, rams babies are tiny), aquarium coop sized nano sponge filter, very little to no extra food build up. 

At first I thought maybe the extra food was creating more ammonia and thus more nitrate. But that is debunked via testing parameters on both sides. Any ideas whats going on?

Edited April 14, 2022 by Cinnebuns

[Wrencher_Scott]

I bet it's light from an outside source like a window. Does that side get more light than the other? Even just a little? Maybe it is the food? It seems there is no way the water would be different somehow. Are the snails like lawn mowers? 

Weird for sure. I don't think you can figure out or second guess algae growth though. 😁

Edited April 13, 2022 by Wrencher_Scott

[Cinnebuns]

On 4/13/2022 at 6:21 PM, Wrencher_Scott said:

I bet it's light from an outside source like a window

Omg that's totally it!  Ty. It does face the window. Also the algae is thickest on the side facing the window. 

[nabokovfan87]

On 4/13/2022 at 4:17 PM, Cinnebuns said:

At first I thought maybe the extra food was creating more ammonia and thus more nitrate. But that is debunked via testing parameters on both sides. Any ideas whats going on?

one side of the tank has more flow because of the intake of the hang on breeder box.  That is one variable.

Second to that, as mentioned above, I would think that there is a window or lightbulb that is causing more light energy on that wall of the tank. Paint it black with acrylic paint or use some of the privacy film / window tint that does not allow light through. (the fish will thank you for it as well)

[DaveO]

You can tell by the cast of the shadow on the towel that there is a lot of light from the left side.

[Cinnebuns]

On 4/13/2022 at 6:42 PM, nabokovfan87 said:

Paint it black with acrylic paint or use some of the privacy film / window tint that does not allow light through. (the fish will thank you for it as well)

I have some black poaster board that would work well for that. Ty!

[Wrencher_Scott]

On 4/13/2022 at 4:47 PM, DaveO said:

You can tell by the cast of the shadow on the towel that there is a lot of light from the left side.

Nice catch detective!