Personally, I would have gotten completely rid of the sand and gone with a better substrate for the new tank as long as you were starting over. I use 100% Flourite in all of my tanks, which works great, except for some of the grasses, which get uprooted by my weather loach because they have such shallow roots. If I thought it would help, I'd take him out of the tank and give him a spanking, the naughtly little bugger.
Two 1 GA desktops, a 5 gallon, a 2.5 gallon, a 10 gallon, a 20 gallon, a 25 gallon, and two 75 gallon tanks, all planted.
I am an expert on algae, so ask me if you have questions. I know how to grow it, just not how to get rid of it.