Algae doesnt need light to grow ... it does help a bit though. My python (for changing water in fish tanks)literally never sees light ... however once a month I have to clean the algae out of it.

As long as you are watering them out of a city water system (that has chlorine or chloramines in it) it will slow the algae growth. But with any water source algae will eventually grow, clear tubing would make it easier to see rather than waiting for the algae to block a drinking valve.

Bryan