UV Flow Question

aaron186 · May 23, 2023

I have a Reefer 425 (112 gal) tank that I have plumbed with dual return pumps. My first return is a COR20 plumbed to a Pentair 25 watt UV sterilizer with an apex flow meter. My second return is a cor15 plumbed straight to the tank.

The Pentair recommendation for flow in my tank is 472GPH for algae (max 788GPH). Rec for protozoa (not my main goal) is 79-130.

I have found that running my COR20 at a level to hit 472 gph (around 35%) is too strong for my display tank to handle. I'm not sure if the flow meter is accurate but it's a lot of high pressure water coming out of the return line. Plus with the second return running on low, I am draining the return section faster than my drain/sump can handle. I have found that turning my COR20 down to about 20% gives me about 380 gph on the flow meter and my tank seems much happier albeit fast moving water in the sump. I have the COR15 turned down to 10% in both cases.

Is running a flow of 380 gph to the UV going to provide benefit to my tank? Does it matter if my flow falls in between the two recommended ranges for algea/parasites? I understand that water needs to be moving slower for the UV to have contact time to kill protozoa, but does the water moving slower alter how it kills algae?

Thanks for you help

EeyoreIsMySpiritAnimal · May 23, 2023

aaron186 said:
I have a Reefer 425 (112 gal) tank that I have plumbed with dual return pumps. My first return is a COR20 plumbed to a Pentair 25 watt UV sterilizer with an apex flow meter. My second return is a cor15 plumbed straight to the tank.

The Pentair recommendation for flow in my tank is 472GPH for algae (max 788GPH). Rec for protozoa (not my main goal) is 79-130.

I have found that running my COR20 at a level to hit 472 gph (around 35%) is too strong for my display tank to handle. I'm not sure if the flow meter is accurate but it's a lot of high pressure water coming out of the return line. Plus with the second return running on low, I am draining the return section faster than my drain/sump can handle. I have found that turning my COR20 down to about 20% gives me about 380 gph on the flow meter and my tank seems much happier albeit fast moving water in the sump. I have the COR15 turned down to 10% in both cases.

Is running a flow of 380 gph to the UV going to provide benefit to my tank? Does it matter if my flow falls in between the two recommended ranges for algea/parasites? I understand that water needs to be moving slower for the UV to have contact time to kill protozoa, but does the water moving slower alter how it kills algae?

Thanks for you help

I can't answer your main question, but the faster flow for algae is to keep up with reproduction rates. Idk if 100 gph will make a difference.

Gundy · May 23, 2023

From my understanding, for parasite control you want the flow through your UV to be 3-4 times of the tank volume. So at 380 gallons per hour you are good because for parasite control (ick) you need the flow to be slow. For algae control you will need the flow to be substantially faster.