Dark patches that show up on top of my Pennywort leaves. I can rub them off a little, but not entirely - the parts "deepest" in the leaves sticks.
Algae 2: In the pictures it looks like white fuzz, but from above it looks like reddish-brown fuzz.
I have a 5-gallon tank, heated at 79*. Light is a Sylvania 6500K 13W bulb, on for about 10hrs/day. I do 50% water changes 1x/week. The tank is home to one betta (though right now he is floating in quarantine). I dose with Flourish 1x/week (day after water change). I have a Red Sea Nano filter whose sponges I clean by swishing in the old water during water changes. I have taped brown paper over the filter because green algae was growing in the tubes... I haven't figured out how to clean the tubes yet; I suppose I need to go buy a pipe cleaner. There's also a light dusting of brown on the inside of the filter chamber... diatoms?
How do I get rid of these algae?