One UV for algae and marine disease

Jeremy0813 · Apr 8, 2022

I'm in the process of planning a large build, somewhere around 350 gallons of circulated volume. I will be using the largest possible Pentair UV I can fit in the room I have. I will have 2 return pumps and 2 return inlets to display- 1 pump through UV and 1 straight to display. My goal is minimally 2100 gph between the 2 pumps, I have sized the pumps accordingly (One pump will have the ability to maintain this rate at the height of my display inlets). My idea was to use both pumps 24/7 but the one through UV at rates suitable for algae through the day and rates suitable for marine disease during the night period. The other pump straight to display would change speeds to maintain the turnover rate so a constant flow is always maintained through the system. Is this a good idea for trying to sterilize both or a total waste of effort? Hopefully someone with knowledge of algae and marine disease reproduction rates could give me a reasonable answer as to why or why not. I'm also considering a 2nd UV for other pump as well....but if this method would be mostly sufficient it would save some plumbing and cost.
From what I've read most algae needs light to reproduce so why not try and hit the protozoa etc. at night? I believe there would be some other benefits as well to this method outside of sterilization. Such as variable flow pattern into display, little easier on pumps during different periods, etc.

Timfish · Apr 9, 2022

To start, running a UV intermetantly on a daily pbasis will probably work fine for algae but is not going to be effective on ich or velvet as ether will be parasites survivng and finding fish when it's off. Personally I wouldn't plumb a UV into the return lines. For one, it's not needed long term and only acts as a heater if run long term. I've found a UV to be far more effective if it is run on it's own closed loop with a appropriately sized supply pump located behind the aquascaping at the bottom of one end of a tank and the return located at teh top opposite end, this seems to maximise the intake of larva to the UV. FWIW a UV on a quaritine tank is a much better way to deal with ich and velvet IMO

Jeremy0813 · Apr 9, 2022

Timfish said:
To start, running a UV intermetantly on a daily pbasis will probably work fine for algae but is not going to be effective on ich or velvet as ether will be parasites survivng and finding fish when it's off. Personally I wouldn't plumb a UV into the return lines. For one, it's not needed long term and only acts as a heater if run long term. I've found a UV to be far more effective if it is run on it's own closed loop with a appropriately sized supply pump located behind the aquascaping at the bottom of one end of a tank and the return located at teh top opposite end, this seems to maximise the intake of larva to the UV. FWIW a UV on a quaritine tank is a much better way to deal with ich and velvet IMO

Thanks!
I'm just considering that for proactive measure against marine disease not necessarily to treat. If I was to have something breakout I would definitely run UV at appropriate rates to help, I do realize that has limited effectiveness.

I've been running a Pentair UV 24/7 on my current set up for close to a year, no problems with heat so far. But I did experiment with flow rates and algae growth on glass. So I personally have not tried it with a standalone pump. But there is definitely a noticeable difference in growth when pumping 4 times turnover versus 6+ in my system. So my thoughts are that a lot of tanks aren't actually getting the turnover that's presumed, I do have a flow meter in line. I had to modify plumbing to actually get rates up to 6+ times turnover, I'm currently using a Varios 8 on a 92 gallon system with about 70 gallons of circulating volume . Point I'm trying to make is that the water from the system doesn't actually go through UV enough times before the algae has had time to reproduce. Which also has to do with sizing of UV as well as flow from wavemakers that actually get everything into overflow over a period of time. Which making a standalone as you mentioned possibly more effective, plumbed straight in and out of display. Good stuff thanks again.

Timfish · Apr 10, 2022

Yeah, flow is a huge variable in controlling anything and I've often encountered aquarists trying to get as high a flow rate through a UV as possible thinking it would deal with stuff faster. I've only used UVs to deal with ich and velvet and along time ago settled on 1-2 turnovers per hour (I'll use a gallon container to check it). My main reasoning for placing an intake at teh bottom behind aquascaping was it seemed that was the most likely place larva would be finding fish and attaching themselves. Seeing ich clear up in established tanks after it was introduced made me wonder about the lifecycle. Certainly resistance of the fish played a factor but it seems like there was more to it. Thinking about the life cycle and an adult that has dropped off a fish has to find a place to attach and develop larva it seemed the most likly place would be behind stuff where there is less competition for space from algae and biofilms as well as reduced liklyhood algae eaters will removed them before the larva are released. Since many fish hide behind aquascaping and are less active at night and flow is usually reduced it seems that's a better place to try to reduce the larva count.

Jeremy0813 · Apr 10, 2022

Gotcha, makes sense that it would be the best place to remove larva. I'm seriously considering the addition of extra bulk heads solely for UV, although I am slightly concerned with putting one too low in my system due to possible leakage of a large volume of water. I'm a firm believer in them for algae with the experience I've had so far. I will probably go ahead and install 2, the Pentair HO 80w is most likely going to be my choice. One stand alone for disease and 1 inline on one of my return pumps for algae. The stand alone will also assist for algae, you can't overexpose algae right! So one would be at roughly 1200 GPH about 4x turnover the stand alone at 5-600 GPH which is about 2x per hour turnover. Sounds like a good plan anyhow.

mindme · Apr 10, 2022

Personally I just have mine setup for ich, since I have ich in the tank. I do not see the need to use a UV for algae because my water is clear. And if I needed to adjust it for some reason, I can do that.

But even at slower speeds you'll still be killing algae in the water. The reason for faster speeds for algae is just so that it can kill them faster than they reproduce. But it's not common to need this for longer periods of time.

Seems to me 2 pumps would just be a waste of money, but it's not going to hurt anything else.

Jeremy0813 · Apr 10, 2022

Correct, reproduction rates on algae are why I was shooting for higher turnover with main pump and still getting satisfactory exposure time.

I'm going with multiple return pumps for redundancy primarily. With a tank this size and livestock that will be involved I'm going for as many fail safes as possible. I figure spend now save later. One extra for the UV will be additional but I don't have to blow the budget with it either.

On the subject of algae, its proven to me to reduce my glass cleaning on my current system is why I would choose to treat continuously. I don't run a low nutrient system either.