black algae

So I recently started up this tank, it was at first a 6.5 gallon tank, everything was fine and the plants were actually holding steady, but the tank cracked cause it was cheap plastic, and now that I've transferred everything over to a new 10 gallon tank all of my plants are turning see through...

BBA was getting a bit out of control so i decidet to try H2O2 for the first time in my tank.Removed all the fishes and applyed 15ml or 4 teaspoons for my 10gallon tank.The problem is that i waited 20 min and nothing happend , no bubbles nothing... Think that the problem must be the hydrogen...

Hey guys, I recently purchased another tank from the local classifeds and one of the plants is covered in black algae. Whats the best way to get rid of it and will it spread if I put the plant in my 75g?