Sprouting trays also come in stacked form. By stacking you can grow various types of sprouts simultaneously, hence allowing for a continuous harvest. Generally they come with an ingenious irrigation system with drainage holes, so you can water the complete tower at once. While still keep a thin layer of water present on each deck.
A common problem is that these drainage holes get clogged with slimy seeds. When you use larger seeds (like mung beans for taugé) you can prevent this from happening. Note: Some germ seeds must first be fully immersed in water, otherwise they won’t grow as good as they should.
The towers come in two materials: stone and plastic.
The plastic towers are usually cheaper and have specific advantages over the stone variants. Whilst you can see through the transparent material it is easier to keep an eye on how the germs grow. Next to that cleaning a plastic tower is much more easy to do, some of them can even be put in a dishwasher.
Stone germinating towers are sometimes made of terra cotta-like material. (not listed here, try and look for Terra cotta GEO sprouting towers). The great advantage is that this material can hold moisture for a long time and thereby prevent the risk of sudden dehydration. The major drawback is that they are very pricey.