Hi, As a bit of background: I'm really new to the hobby, but I've done a lot of reading. I currently have a 5gallon freshwater tank, planted (although not heavily-- just anubias nana, staurogyne repens, and cryptocoryne of some kind). I am partway through the nitrogen cycle (as of today, my ammonia was 0.25ppm, nitrite 2.0ppm, and nitrate a GENEROUS 5ppm but probably somewhere between 0 and 5ppm). I dosed 2ppm of ammonia (using Dr Tim's aquatics ammonium chloride) 24 hours before testing today, so I'm feeling good about the progress of the cycle (especially since I hadn't expected to really get going on the cycle for awhile yet-- I was out of town for 5 or 6 days and just dumped 4ppm of ammonia into the tank in the hopes that something would happen while I was gone, and it looks like it did!). (I just re tested ammonia before dosing with ammonium chloride again and I want to tentatively say it's at 0? I'm not great with the color sheet comparison.) No fauna in the tank as of yet, I'm waiting for the cycle to complete, but I will eventually add some shrimp and a snail or two. I have a filter (the aquaclear 20) and I just installed a heater yesterday (the Aquatop digital nano heater). After a mishap where I left the heater's thermometer outside of the tank and therefore had the temperature up to like 90 (luckily, I had an extra digital thermometer running and caught my mistake, but it had definitely been going for a while-- maybe 15 or 20 hours?), the temperature is stable at just under 82 degrees, which I read was ideal for bacteria growth. I have lighting on a timer, but just a lowkey LED clip on desk lamp. I'm using flourite substrate for planted tanks, flourish (dosed weekly), and I put in root tabs when I set up the gravel and filter and such. Ok, here's my question. What the heck is growing on my rock? Is that algae? Something else? It came off really easily when I scraped it with a sculpting tool I had lying around in an effort to fish it out and get a closer look, but it floated away before I could pull it out of the water. There's not a lot of it so I'm not WORRIED, per se, but scratching my head for sure. It IS pretty close to where I pulled out a plant which I suspected of being infected with something (the name of which plant I cannot for the life of me remember). Sorry for the potato quality of these images. It's hard to get a good photo of stuff through glass and water and everything. Anyways, if you got through this whole post, I'm impressed and grateful. Here's my little tank. I know it doesn't look like much. But it's mine.