Can you please elaborate on this? Why is a direct loop better than a manifold install? I'm not clear on what you are gaining/losing.
Considering this as next piece of equipment and its challenging to figure out how to get it plumbed since I'll likely need to cut thru a wall and really want to get it right the first time
thx
Sure thing, but there are a few variables with UV filters to understand before deciding on what works best for you.
UV filteration is based on organism exposure to UV light (made up of UV-A, B and C but that knowledge really isn't needed for this, but very interesting to research). Different organisms require different exposure rates to result in sufficient damage to DNA to prevent reproducing (or outright death).
The only organisms impacted by UV are those that are free-floating at some point in their life-cycle. This includes many of the serious pests we face - ostreopsis dinos and marine white spot for example)
The classifications are broad and there's some bleed over but generally there's algae (that includes dinos) and pathogens (ich). The algae is based on high flow but requires less exposure (usually expressed at uwatt/sec2). Dinos can double in 20 minutes so getting the correct exposure at 8x tank volume /hour is critical if you have an outbreak. Pathogens are more advanced organisms and require 3-5x or more the exposure that algae does. However, pathogens do not reproduce as fast so the flow can be fairly low (few x tank volume per hour).
So as you can probably see, sizing the correct UV/flow rate requires some consideration. How do you get the min 30,000 uwatt/sec2 at 8x tank volume flow per hour for the "algae" as well as getting the high exposure needed (min 90,000 uwatt/sec2) for pathogens?
If your tank is smaller (say under 120 gallons) its fairly economical to run one large UV filter that can do both. BTW 'fairly economical' is upwards of $500-600 or more - what a hobby. A large UV (I don't like the term oversized, although it does exceed manufactures recommendation) will be able to produce the high UV needed for 'pathogens' at the flow rates needed for 'algae' so one pump, one speed set it and forget it (assuming your directing all tank flow through UV filter).
It is possible to us UV only to react instead of preventative. Then you can just have the UV standing by (even if installed) on a variable flow - either variable speed pump or ac pump with throttle and adjust as needed, but you will not have both at same time. This is very reasonable approach, run it for algae (which also provides water clarity) and drop speed if you have some disease outbreak.
Lots of words right? Almost done.
This is why I say it's easiest to have a UV on it's own direct loop - to and from the display tank. You can adjust flow either to the UV for specific issues or just keep it running for both (if sized correctly) and make any changes you want to manifold reactor without impacting UV flow.
If you have it on a manifold - make sure the UV output is going to display and not to sump. Otherwise you'll only get minimal performance as you can't really tell how much tank water is getting exposed. Honestly, for routine clarity without any outbreaks, that might be fine. Then if there's an outbreak, you can just remove the UV filter from the manifold - connect it to a pump with some hoses and drop it in the display tank for a few week.
So in summary...many options exist. Just be aware of how you want to manage the UV filtration; continual or as needed, what you want to manage, 'algae' or 'pathogens' or both, and ensure the flow rate provided and tank turnover through the filter will result in both the exposure needed for the UV filter rating and turnover to keep up with reproduction rates of certain organisms.
You'd think I'd copy this down and just paste it when asked...I really should. Anyways, best of luck. I know it's a lot to take in but I'm a huge proponent of UV filtration. Just buying my new upgrade and UV is key component.
