Are these brand new tanks?
Algae's REALLY common in new tanks.
Other common causes of algae and/or murky, milky water: Not enough water movement, over 10 hours a day of light, over feeding, flucuating CO2 levels (particularly if dosing with Excel), too much CO2, ammonia/nitrites/nitrates.
Milky water is especially common with the ammonia spike in the cycle as dogdoc said and if you're tank is new that's what I would expect as well. If it's not you need to start looking at the other things I've listed here.
Also is it murkey green or murky white? I just finished a battle with green water and the thing that finally broke the green water for good was getting a new filter with a higher turn over rate to create a lot more water circulation in the tank (and also a better filtering process).