Thank you You YOU! *hugs to my crazy Canadian cousin*

Happy happy birthday to YOU YOU YOU YOUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU!

Yes, my cories have actually been very active, way more active than I've ever seen them. They're out in the day now climbing all over the driftwood and fake decor. And the honey gouramis nibble at the algae too.

Thanks again for all your help. :)

So far, the substrate doesn't seem to be bothering the cories or kuhlis so I feel okay leaving it while I look around.

I don't know how long it releases silicates. I've never had it. :D
You'll have to look well for some black or dark sand. Quikrete is a medium darkness.
Have you noticed your cories eating brown algae? Some love it, I realized mine enjoy cleaning the leaves of it.

Yiiiiikes! I had absolutely no idea. And I had no idea Caribsea made their sand from glass. All I know is Black Beauty "sand" isn't even sand but iron slag. Yikes, yikes. I've had it for about . . . 4 months now? When does it stop releasing silicates?

So far, it hasn't bothered the cory cats but definitely worried about the kuhlis. I'll look into switching to play sand. I just hope I can find a darker colored sand than the one I had before.

Thank you so much, Olympia! I never would have figured out the problem without your help.

As for the sorority, I suspect it is due to low light and no plants. I'm going to get some water sprite to float in there.

"The 20g has CaribSea Tahitian Moon (black) sand."
There ya go. As a side note, this sand is labeled unsafe for bottom dwellers- I'd watch the loaches.
All of CaribSea sand is made from glass shards (hence unsafe for soft bellies) and not real sand.
That's where your silicate problem is coming from.
The only thing I can recommend is frequent water changes, eventually it'll stop releasing silicates.
Of course if you want, you can change it out for regular playsand. I might do it for the loaches and algae problem. Since it's NPT you should be able to change it all out at once. However that does mean you'd have to rip it up AGAIN. :(

We did just have our water tested for a bunch of things so I can see if I can find the report on my dad's desk. Hopefully it will say if there are a lot of silicates in the water.

I know high nitrates can cause algae too. I'm somewhere around 20 ppm even with the Clearmax. The plants are still settling in but I'm hoping they'll suck up more nitrates as they settle. I think I might try amanos first since the last batch of otos I got didn't touch the plants. They just darted around like crazy things and sucked on the heater. o.O But if the amanos don't do squat, I'll try otos again.

Thanks, you're the best, Olympia. :D Okay, to answer your questions. The brown algae is mostly in the 20g but there is some in a few of my small, unfiltered betta tanks. In those tanks, I'm pretty sure it's 'cause the tanks have no biological filtration so a lot of nitrogenous waste. I also have a bad outbreak in my 10g sorority which is all plastic plants. The 20g has CaribSea Tahitian Moon (black) sand. The sorority has Petco black gravel.

If I'm not supposed to use a phosphate remover, I'd better get the Fluval Clearmax out of the filter. I can just use a regular nitrate remover.

Amano shrimp are supposed to eat brown algae, but someone told me theirs wouldn't, and they'd just eat fish food when the fish were fed. You could try.
Otos will eat your brown algae, and 3 will add not much bioload. They are vegetarians, so their waste is less and they add less toxins.
I have yet to find a product that absorbs silicates but not phosphates. Byron said not to use phosphate remover in a planted tank since plants need it. However none of us have ever experimented, so it could be worth a shot to try some.
In the mean time, brush algae off plants by hand to help the plants.

I spend so much time researching brown algae, which I don't have, while my tank is overrun with hair algae. -__- Got my priorities in order, that's for sure.

Woo, I'm honored. :D
Okay, questions: do you have brown algae problems in just that tank or all of them?
If all, do you use the same substrate for them all? If not, what brand is the sand in your 20?
Brown algae feeds on silicates, not phosphates like most algae. Silicates could come from the tap or substrate.
If from the substrate, it'll wear off eventually. Frequent water changes are the best defense, to lower silicates constantly.
If it's from the tap, water changes don't help obviously.
I don't know of any common silicate tester, so we gotta go off your other tanks.