I got one, for my 90, its an 8 watt. My tank is in the living room and got a lot of sunlight, resulting in a lot of algae growth. True, I could have prevented the problem by closing my drapes, but I like natural light and so do my fish. It takes care of the green water. It also helps to eradicate sickness in the tank. I was able to add it directly to my return line from my sump. All I had to do was cut the line, and if I decide to remove it, the cost of hose might cost $ 0.50.
The bulb I clean out every couple of months, its never dirty, I am just cleaning everything else so why not
And the 8 watt bulbs, that work for a couple of years effectively, cost me a whopping $9.00 at the hardware store (that I have not had to buy yet). As for the increasing temperature, 8 watts for 90 gallons. Well, I dont know anyone who thinks an 8 watt heater can heat a 90 gallon tank.
BTW. Not only does it work as an after thought. It also works for a preventative, for that 1% when quarantine doesn't work. Stopping contagious disease
bacteria, even Viruses... Or you could just use it to help keep the green water at bay.
just an alternative oppinion.