I soon found out there are specialised articles on the market for these types of tanks, but also that they are well overpriced. I decided to use some of the leftovers to build a DIY Gravel Cleaner after the idea of JBL, found here. (Nice thing about it is that it is square so it can reach the corners of the tank easily)
This article is based on my blogpost on http://hmf-shrimptank.blogspot.com, where I also post the entire DIY project for building a filter for my shrimp-aquarium. Comments and feedback are welcome!
Here are the steps I took:
Step 1: Ingredients
Some tubing of roughly the same diameter
Have some tie-wraps and teflon-tape or plumbers-tape ready
Take a small (transparent) square container left over after the contents have run out. I used a soap-container in my example. I would not recommend to use something that stored any more serious chemicals
Clean out the container REALLY thoroughly as shrimps will die if you don't!!!