Hey dwc bucket

hey guys im just wondering if this is normal and just needs to be cleaned every once in a while or if im doing it wrong.

I just built a dwc bucket. I just have airstones running in them with hydroton as a medium.

I ran the bucket for about 5 days with a dummy plant just too kinda tune things in on my set up. just emptied it and i noticed some kind of gunk build up on the bottom of the bucket and on the airstones.

www.4gp.tw/b039/1411397661521.jpg

wtf is this shit?

Hmm, nutrients maybe? If you added them during your test anyway. If not that, algae I would guess. Is it slimy?

Could be nutrients and it's not really slimy seems more like a build up of something.