i dont
i love ride the hill but still i go in the park and hit things not just slide trough the "pipe", and nile is a great crusing coarse why change it?
ive only put water in mine but once i ran out of water so i filled it with stream water, but i was able to kill that algae.
my old hydro pack never had algae problems, and i would let water sit in that for weeks.
update on algae growth
i have been soaking my hydro pack in Dawn soap since i stared this thread and it has at least doubled the amount of algae in the pack I have also scrubbed it with a sponge and still the algae remains. so following the advise of my mother i am now soaking it in vinegar.