6.6 Bookshelf Aquarium Dark Green Algae - nutrient imbalance?

I have a 6.6 gallon bookshelf aquarium that is struggling with what looks like dark green algae at the edge of plant leaves. It's been running for 4 months with plants, I added shrimp 2 months ago, and 6 pygmy corydoras and a nerite snail 1 month ago. I use remineralized RO water for 20% weekly water changes. Parameters are as follows:
pH 7.4
Ammonia/nitrite/nitrate 0/0/0 - yes it's fully cycled, plants just keep nitrates at 0
GH 8
KH 5
Phosphate 0.5
Temp 76 F

I use the 24" hygger Advanced Full Spectrum LED Aquarium Light with 24/7 Lighting Cycle and use the 24/7 lighting cycle

A few weeks ago, I started using the NilocG PPS PRO system where you mix the dry ferts into 2 solutions, a macro and micro and dose daily.

Here are photos of the full tank, and close ups of the plants. You can see the dwarf hairgrass is covered in dark green and the bacopa is losing the lower leaves. The wisteria is also dark green at the edge of the older growth, the new growth is bright green. Also, the plants get covered in little air bubbles in the afternoon every day. Is that normal?

What should I change to get rid of the algae? Less light? More fertilizer?

 

Does this stuff rub off easily and does it feel kinda slimy? If so then it isn't an actual algae. It is cyanobacteria. (blue green algae) Get some UltraLife Blue Green Algae Remover. Follow the directions for 2 doses of it and this stuff will be gone. I have used this product and am very comfortable recommending its use. It didn't harm anything in my tanks other than the cyanobacteria.

 

Does this stuff rub off easily and does it feel kinda slimy? If so then it isn't an actual algae. It is cyanobacteria. (blue green algae) Get some UltraLife Blue Green Algae Remover. Follow the directions for 2 doses of it and this stuff will be gone. I have used this product and am very comfortable recommending its use. It didn't harm anything in my tanks other than the cyanobacteria.

No, this isn't cyanobacteria. I've dealt with that stuff before and am familiar with the slimy sheeting texture of it. This is more of a powdery dark green stuff that is hard to remove. It's all over the plants, on the sand, and on the walls of the tank. The neocaridina shrimp I've got in the tank seem to eat the stuff, but there's way more than they could ever eat, and it just keeps growing.

I'm wondering if the 0 ppm nitrate is part of the problem. I dose potassium nitrate, but my level is always 0 in this tank. I know that my test kit is good because I get higher readings on some of my other tanks. I'm new to planted tanks (other than the super easy plants I've kept in the past with just root tabs) and don't quite understand the ideal parameters for keeping them healthy yet.

 

I am not sure what you are dealing with but I do understand your frustration. It is strange that you are seeing no nitrates but not unheard of 'specially in a planted tank with a low bio-load.

The first thing I would do is much bigger water changes. Something is out of balance. Quite often water change can help balance things out. With you just changing out 20% of the water each week the things we don't test for are gradually building up in our tanks. Some of what is building up may be unused ferts. We remove 20% of the buildup but are leaving 80% of it in there. I would gradually build up to doing 50% weekly water changes. I do that to my tanks each week and then once a month I change out at least 75% of the water. I consider this bigger water change my reset.

Since it seems you have tried many ways to put a stop to this. Hopefully the bigger water changes to dilute the food feeding the algae will put a stop to it.

 

I am not sure what you are dealing with but I do understand your frustration. It is strange that you are seeing no nitrates but not unheard of 'specially in a planted tank with a low bio-load.

The first thing I would do is much bigger water changes. Something is out of balance. Quite often water change can help balance things out. With you just changing out 20% of the water each week the things we don't test for are gradually building up in our tanks. Some of what is building up may be unused ferts. We remove 20% of the buildup but are leaving 80% of it in there. I would gradually build up to doing 50% weekly water changes. I do that to my tanks each week and then once a month I change out at least 75% of the water. I consider this bigger water change my reset.

Since it seems you have tried many ways to put a stop to this. Hopefully the bigger water changes to dilute the food feeding the algae will put a stop to it.

I was under the impression that shrimp can't handle larger water changes. Instead of larger changes, would several smaller changes per week be better?

 

I was under the impression that shrimp can't handle larger water changes. Instead of larger changes, would several smaller changes per week be better?

Two or three water changes a week would accomplish the same thing as the bigger one once a week. Bigger water changes do have to be done a bit more carefully than if just fish were involved. When we have both fish and shrimp we have to take both into consideration. If the tank is well established bigger water changes can be done even with shrimp in the tank.

I have a shrimp only 2.5 gallon bowl. I do my normal 50% weekly water changes in this bowl and 75% once a month. When doing the water changes I make sure the parameters of water I am replacing is as close to the water I took out as I can. The only difference in my case is the TDS level. It is lower in the fresh water. I control the number with Equilibrium. pH is the same as is the temp. I don't pour the water back in the tank, I drip it in. It can take more than an hour to refill the bowl. I use a length of air line tubing with a control valve on the bowl end of the tubing. With it I can control how fast or slow the bowl refills.

As long as you match the parameters bigger water changes can be done even with shrimp in the tank.

BTW: I have cherry shrimp. Some other species may have to be handled differently. If you have cherry shrimp they can handle larger water changes.