Cristal ponds work very well, I build one for my snake. The algae only grow when the terrarium is exposed to direct sunlight, if you change the water in the "pond" at least once a week you should have no problem, although I recommend changing the water more often. Putting plants is also a good idea, they create shade over the pond and prevent algae from growing, also they clean the water and take care of them is not difficult.

P. D. I love that site, storm the castle, that guy does almost everything .