Cant believe this! I was cleaning my sump and moving the ballast to make room for my reactor and I've never really looked at the ballast, just knew it was a Hamilton. Well I now know that its a M58 probe start so I guess Radium or any thing else that needs electronic is out. Not only that but its only a 175 watt that I have been putting 250 watt bulbs in. My wife bought the whole system used and the guy installed it and I never realized it. Its been this way for 2 1/2 years. Do I change the whole $y$tem or will 175 watt bulbs be enough for a 75 gal tank? Whats the best M58 probe start bulbs ? I was thinking of going back with the Hamiltons.