you can get them for anywhere from $5 to $20 at Walmart, etc. in my experience, most of them suck and won't keep the right time for s*!t. I have the Coralife powerstrip. it is more costly than most timers, but in 8 months, it hasn't missed a beat and keeps perfect time. If I'm not mistaken, it has four outlets for 24 hour a day use (filters, powerheads, etc), then is has 2 outlets for night and 2 for day. the only problem is that if your light fixture has more than one control for different bulbs, you'll probably need two of these timers. but that's probably the case with any timer.