Originally Posted by shadowfax33
Is there a specific volume of water that it should cycle per hour? How would you judge what sized unit to obtain for a given volume of tank space (Have a 90 gallon tank w a sump). Can they be placed in the sump? Do they come w a pump or must you buy a powerhead? Any brands generally considered reliable? What's "Dual Mount" Vs "Inline Only"? I assume "Twist" refers to the water twisting in the unit. Do they come w the bulbs or must you buy them serperately? Thanks for all your help Pasfur.
First, let me address the common myth, that UV's harm bacteria populations and kill copepods, etc.
UV's only kill what is free floating in the water. The LARGE majority of beneficial bacteria, copepods, amphipods, and other such critters are not free floating. They live on and inside the rock and sand bed. I have never noticed any relevance when using UV as to these issues.
Yes, a UV can be in the sump.
Most require a power head.
As to brand, it is just light bulb, so I have never purchased an expensive unit. I generally go low budget on my setups and replace what is necessary as I go along. This has never been an issue and I have never spent over $100 ordering a UV from Aquarium Supplies, Pet Supplies and Pond Supplies by That Fish Place - That Pet Place
Inline means it designed for sump use, basically. Water flows "inline" thru the UV on its way to the sump, or skimmer, etc. Dual Mount can be used inline, or can hang on the back of the tank.
Twist refers to the pattern of water flow. A unit that twists inside the chamber has longer exposure. These are usually compact in design.
They generally include a bulb. I would buy several extra at time of purchase. I have experieneced difficulty in purchasing replacements. It can take a few hours of searching online for a compatable bulb if a unit is no longer made.
Gallons per hour? Not sure the standard answer. I have always used a MaxiJet 250. I want slow flow for longer exposure.