how much colorant would you need to put in a 25 acre lake to stop germanation of coontail and waterlillys? the damn is four hundred foot wide with a maximan dept of 12 feet.

Think it over. The stuff does stop the photosynthesis that the plants need but it also disrupts the light penetration that the phytoplankton needs. Without light penetration, gamefish eggs don't do at all well.

Instead of colorant, I had mud a couple of years ago that precluded any light penetration. So, no forage spawn and no bass spawn.

cadams, what are the pond goals? big bass?

dave gives good advice, but a natural follow-up question is "what are some options besides using colorant?"

i'll try a few, and then maybe some experts can expound:

manual removal
herbicides/chemicals
fertilization
aeration

this is not to say you wont end up using colorant, but other options should be explored before dumping in dye and potentially disrupting the food chain.

We have 10# bass in the pond now, but the coontail has taken over the pond. I sprayed the lily's which is going to take a couple of years to get under control. I've removed TONS of coontail to only have it regrow in a couple of weeks some seemed like just days.
I thought of fertilition but and unsure it will not make the matter worse.

cadams, a mix of Reward and cutrine plus is very effectice against coontail. Another alternative would be to stock 7-15 grass carp per acre.