Hi there i know a few people who have used white vinegar to clean tanks, removing solvents and built up algae, but not sure on if this can be used on acrylic but dont see why not, afterwards i'd get some sterilising tablets, like the stuff used for babies bottles etc, give your tank a good wash round with this then thoroughly rinse with tap water, then being me id go another thorough rinse with ro water.
Hope this helps.
Hi again been chatting with a fellow reefer of mine and asked him about cleaning acrylic, he said to use vinegar and mix it 50:50 with water to clean, as putting it on neat can craze the acrylic. He has done a few acrylic tanks this way with no problems.
If you are a bit apprehensive you could always do a weaker dilution.