ok algea problems come frome something. you must eliminate the problem and not try to mask it.
ask yourself.
1.is there any direct sun light hitting it?
2. do you use tap water?
3. am i overfeeding the tank?
4. do i have my lights on too much?
5. is your tank really young?
6. are my powerheads under powered for the size of my tank?
7. i dont have a proper clean-up crew.
if you answered yes to any of those questions change it and reavaluate the situation in a month or two and then ask your self did my algea get anybetter? you should know that the amount of snails vrs. crabs is a varying opinion. if you corriline algea is slow then try more snails and less crabs and mix up the types of crabs. i have good results with blue legs but there are alot of people that dont like them because there are holy terorrs when the want to be.