Safe paint for concrete block pond?

For several months now I've been working on a small koi pond for the
back yard. The shell is formed out of concrete block sitting on a 6"
thick concrete slab. Total capacity of the pond will be about 1300
gallons with a small waterfall at one end and a skimmer at the other.

The concrete block work is now done and I'm turning my attention to
painting. Knowing that concrete block is porous, and will raise the
alkalinity of the water, I need to find a good paint to cover
everything with. My first thought is to use swimming pool paint as it
is designed for constant water exposure.

Has anyone had any experience with the "Smart Seal" line of paints
(http://www.smartsealco.com/pool/)? They have epoxy, acrylic enamel,
and synthetic rubber products. This brand caught my attention because
it is carried by a local vendor.

I contacted the company via e-mail to ask if their paint is approved
for fish pond use. Their reply was that it is not approved for fish,
but that they have heard of people using it. My guess is that they
have just never gone through any type of formal testing for that sort
of application. Still, considering that a swimming pool has people in
it, you wouldn't think the paint would be allowed to leech toxic
chemicals.

Has anyone used this or another brand of pool paint in a koi pond? If
this is not a good idea, I'd really like to hear of some alternative
coatings which I can get in the Eastern US.

Thanks!