what is it?

Hi everyone! I've had this tank for close to a year now and recently this algae has popped up. I've undergone multiple water changes, but it keeps coming back. What is it and what can I do? Thank you so much!!

My 1 year old male guppy has a weird lump in his tail. It is pretty big. He doesn't act like it's affecting him at all. He has had the same tank set up for 2 years it's a 20 gallon. They eat a variety of froazen brine shrimp, brine shrimp dry, algae flakes, and fish flakes. Any ideas to what...

Alright, about a year ago, I bought 4 cories from a LFS that is very poor at identification...  3 were in one tank marked "large cory" and the smaller one was alone in a tank marked "small cory".   At the time, I thought they were all trilineatus, but the one was younger than the rest... over...