We have 5 saltwater tanks in our house. 2 of them are 29g biocube. We really like the biocubes. Pretty easy to take care of, don't take up a ton of space, and they look nice. Around here you can find a new biocube (older style lights) on sale for $250. Doesn't sound like too bad of a deal if it comes with the stand (and you need it), skimmer, etc. We bought our second biocube used and had some problems with it, a small leak, fan not working, needed new lightbulbs. We should have checked it closer because it would have been cheaper to buy a new one. We don't have the stand that comes with either one of our tanks, you may not need it. Also not too impressed with the skimmer, we are going to upgrade to a better skimmer. I would check the tank carefully first and maybe try to talk him down a little bit. JMO
I had taken my larger tank down for a few years due to time, money, little kids etc. I wish I would have known about the biocube back then because it would have been perfect for that time in my life. Even though you are limited to what you can put in it, I was amazed how much it was actually able to hold. You just have to be smart about what you put in it. I think it would make you a nice starter tank.
