What were your biggest purchase mistakes?

[viperfish]

TEK Light Fixture has to be the most poorly built flimsy thing I've ever seen. The flimsy piece of acrylic that's a poor excuse for a bulb protector. The legs and hanging kit they charge you extra for... all crap.

UV Sterilizer Didn't do a damn thing.

Maxi Jet Sure Flow Mod Kit Crappy rattling POS... junk.

Skimz Skimmer First one arrived with a broken body. Second body had the holes in a totally different place so nothing on the first matched the second (without drilling). The pump sounded like a turbine running in my cabinet. In order to get it started I had to blow into the air line or all it would do is chug and rattle. It took two skimmer bodies and two pumps to get one working skimmer. It looked really cool in the pictures... that's about it.