Non-toxic dye to observe water flow in reef

I have a chiller circuit for my 150 gallon reef which pumps cooled
water back into the tank at about 600 gallons an hour. The tank was
designed poorly in that with the hood on, I cannot access 2/3rds of
the tank. Further without someone else to help me take the hood off I
cannot access that portion of the tank. The 1/3rd of the tank that
I can access has a MH pendant over it, and I have that portion of the
tank pretty well saturated with corals, with no room for additional
organisms. Bottom line is that I would like to add some more corals
to the difficult access sides of the tank which do not require alot of
light, and perhaps are filter feeders ( sun coral, Coco worm perhaps,
non-photosynthetic gorgonians) Such organisms are considered to need
regular feeding (and perhaps even directed feeding) to survive for
long in captivity. The chiller return enters the tank on the least
accessible portion of the tank. I was thinking of placing filter
feeding type organisms around the chiller return, and adding foods via
the chiller circuit. In order to optimally place organisms, it would
be great if I could observe how the water flows out of the chiller
return into the tank (comes into the tank from a 1/2" pvc pipe at
about 8" off the bottom of the tank). Anyone know of a safe dye that
can be used for such a purpose. I of course would not want to do this
unless I knew it would not be toxic to my reef tank.

The problems I see with the dye are, dilution and cleanup. If you used any
water soluble dyes it would dilute pretty quickly in that volume of water. And
once its spread over the tank, how do you remove it?

A quick thought that might work, tie a plastic ribbon (like the ones they use
in construction to mark property lines etc) to something you can drag around
your tank, rigid airline tube, what have you. You should be able to see
direction and the power of the current in that way.
~John

"Timothy Tom" wrote in message om...
[..] the chiller circuit. In order to optimally place organisms, it would
be great if I could observe how the water flows out of the chiller
return into the tank (comes into the tank from a 1/2" pvc pipe at
about 8" off the bottom of the tank). Anyone know of a safe dye that
can be used for such a purpose. I of course would not want to do this
unless I knew it would not be toxic to my reef tank.

Why don't you use some fine frozen food instead of dye?
Get a packet of frozen brine shrimps babies, unthaw them, and
do your test feeding. You will see how the food is distributed!
Brine shrimp babies are orange dots visible to naked eye.

BTW - You could also use green dye in a form of phytoplankton :-)))
I know for sure it is safe and not toxic - I use it to feed my tank
every other day ;-)