I ran accross some cheap "submersible" UV lamps for the aquarium and got some. They have "no" outter cylinder (similar to common submersible heaters) and must be placed inside a filter box so fish are not exposed to them.
I see no problem using them because I have room in the sump where I plan to keep them between filter pads. However, 3 different sellers suggest using them for 2 hours a day max, and only 4-5 times a week. I asked why not 24 hrs a day and was told that would be bad for the fish and the lamps. I can see it'll shorten the lamps' life, but bad for the fish ??? Can't understand.
I see no problem using them because I have room in the sump where I plan to keep them between filter pads. However, 3 different sellers suggest using them for 2 hours a day max, and only 4-5 times a week. I asked why not 24 hrs a day and was told that would be bad for the fish and the lamps. I can see it'll shorten the lamps' life, but bad for the fish ??? Can't understand.