[dwalstad]

I assume that this is the 90 gal tank you wrote about earlier.

The UV light probably would cause photoreduction of DOC-bound iron and make it more available for uptake by both plants and algae. However, removing the floaters could have made a major contribution to a sudden explosion of staghorn algae? And the H2O2 treatment hurt the plants, so that they leached out their nutrients to further feed the attached algae. So it could be that any one or all of 3 factors were operating here. That said, I doubt the UV had that much effect. (Rooted plants should be getting their iron from the substrate.)

Do you know what the GH and KH is in this tank? What is your water source? Does house have a water softener (ion-exchanger)?

 

[dwalstad]

Yep this is my 90 gallon.
GH is 140 PPM and KH 50 ppm in the tank.
Source water for the house tests at 160ppm and 110KH. I do have that Controsoil substrate cap which does lower KH/pH, so could explain that, or I didn't flush the house one time/bypass the softener.

Thanks for Info. It sounds like the GH and KH are okay.

I would stop any H2O2 treatment.

If you want to play around with something that won't hurt your plants, I would add KHCO3 (potassium bicarbonate) to get the KH up a little. I've been dosing 1/2 teaspoon per 10 gal. I used to use baking soda (sodium bicarbonate) to increase KH. But adding K is definitely better than Na for plants. (I bought a pound of the crystals on-line for about $20-25 from folks that sell nuts--'Nuts.com' .) Furthermore, aquatic plants that use bicarbonates (50% of species) as an alternate carbon source generate a high pH on the top side of their leaves (pH 10 to 11) due to biogenic decalcification. One premier scientist speculated that this high pH on top of the leaves could inhibit attached algae. I agree. But no one has ever tested this as far as I know.

Carpet plants are always a problem in a tall tank. They need light but they're at the bottom of the tank not getting that much light. It's tough for them.

Lots of variables here. But if your other plants are doing well, the tank might stabilize on its own.

 

[dwalstad]

I am having the same problem.

The problem is with attached algae? Would like to see a picture of this?
If you clean out the filters, you'll get more flow. (Canister filters can go anaerobic and cause major problems when they get clogged up.)

 

[dwalstad]

Ugly looking algae! Meant seeing a picture of the entire tank setup, so we can get an idea of plant biomass, plant types, how many plants are infested, etc. Your plants look relatively healthy, so if the algae is only on old dying leaves, it might be that big a deal. Just remove old leaves.
The low GH could be a factor, but you could have other issues. Recipe for increasing GH is in my book (p. 87) or in this earlier thread.

 

[dwalstad]

View attachment 76352

In this picture you have a mixture. Java Moss is at the top of photo. Notice deep green color and multiple tiny side branches. On the extreme right, you have a few strands and coiled threads of Staghorn algae. Notice no little side branches.
It looks like some of the Java moss has turned grey from the treatment and is dying.
Folks I don't recommend treating algae with chemicals (Excel, H2O2, etc0. You just injure your plants and they release their nutrients into the water. Even if you kill the algae, the dying algae and plants just releases more nutrients into the water to stimulate more algae.