I think what he was trying to allude to was that this hobby is expensive and you should prepare for that. The way I took it, I believe he was just saying make sure than you plan your hobby expenses accordingly or else you'll end up spending money you don't have on your tank.
Myself for example. I consider myself quite diligent with money and have every dollar accounted for at the beginning of each month. My monthly budget for Aquaria is $200. However, this hobby is super addicting and I started pulling my grocery money into buying aquarium stuff. My tax return bought a light, etc. I've gotten back under control, but 8 months and $3,000 later, and I see no real sign of slowing down yet.
Make sure you hold yourself accountable for a budget and you will appreciate you success a whole lot better!