Well, I'd like to prevent this problem if possible and I guess I'm prepared to do a little actual maintenance.
The bulbs have been in almost 4 years. One out of the 4 is on tonight. I guess I should replace those. I think I changed about 40% of the water 6 months ago. Haven't cracked the filter open in over 2 years (really bad when you consider I've actually broken down the tank and moved in that time).
Aww gee. Now I feel like a terrible pet owner. Maybe I'll look for my test kit.