You could add a fish that loves mesquito larve. Most do! Otherwise you can net as many out as possible and as a last resort treat the tank. As for the algae if you've been gone I take it no ferts or WC's have been done and how long were the lights running daily? I'd only run my lights about 6 hours right now, do a couple good WC's, get your fert's back on track and possibly treat the tank with H2O2 and or Excel. Do you know what kind of algae it is or can you take a picture?