[DiverDude]

What can ye do ? -indeed !

The reality is that you have limited practical options. As others have suggested, the *threat* of something legal (that may or may no be practical given the time it would take and the amount involved) is probably your best approach. Be sure to work the angle that you know he's working illegally (no business licesnce etc.) and it's unlikely he's got WCB and the like. These can all cause him SERIOUS issues and fines that the province WILL extract from him !

If you sound convincing and appear to know what you're talking about AND he's not well versed in this sort of thing, then he may roll over and pay you to avoid legal problems. In the end though, if he calls your bluff, I'd think that for the dollar amount, it's not worth your time to pursue -legally. If you're half as good a carpenter as you are aquarist, you can make more money in half the time it takes to chase this douche.

Frankly, if it came to that, I'd be looking to extract a pound of flesh in some form or another.

The moral of this is, unfortunately, that the days of handshake deals are largely gone. Some sort of written agreement would go a long way right now -but then, it'd only be really useful in court and you really want to avoid that hassle.

Best of luck.