Depending on the specifications you need
(submersible?)
This looks pretty nice if you happen to be in Germany:
http://www.amazon.de/dp/B000OY2BQ8/
http://www.amazon.de/dp/B008TL1QYQ/

If you want an economical 230V Europlug, 320 GPH (with even adjustable flow rate) pump from Chinese, you can buy this on eBay for 11.30 ⬠(and this includes free shipping to Belgium), probably the same thing we pay twice as much in USA:
http://www.ebay.com/itm/111075558613

Good luck

PS By 'dirty water' I assume you mean soluble fertilizer solution. If there is a difficulty with larger particles and other garbage, then you need at least a crude filter you can include into your design easily when using these type pumps.

PPS If you are visiting Amsterdam, just ask at the "coffeeshops" where they buy their pumps to grow their hennep (Probably there are cheap Chinese made pumps available, similar to the small submersible pumps we buy for poor men's vegetable crops here in the USA). I speak with zilch experience, in this department, but it sounds logical and worth investigating since you just need the pump for your vegetables.

This post was edited by PupillaCharites on Tue, Aug 6, 13 at 0:11

Thanks a lot for your reply. These pumps seem good and I'll probably use them in my next hydroponics system.

Glad to be able to return some Tyrolean hospitality ;-)

Please let us know how it goes. If you are building that concept design, be sure to make opaque (block light) from all light ==> water or algae can grow in your clean system. If you can shine a flashlight on one side and not see it very much on the other side it's ok.

It's too bad the interesting root zone is so shy...
Cheers!

Thanks a lot for your reply. These pumps seem good and I'll probably use them in my next hydroponics system.

Not sure why I seem to have posted the same thing twice, but anyway - that's a good point I'll bear in mind. I'll keep you up to date on how things are going. To be honest I'm still planning the room where all the systems will be to make the most out of its limited space. I hope to start building soon.