I have water distillers and I use these to hold the siphon hose against the walls of the fish tanks
They work very well and I'm 100% happy with the product and the price!

These little suction cups are a must-have for any aquarium enthusiast, and at $2.00 for 20 (free shipping), Amazon's price was better than anywhere else. The little cups can hold hold air line tubing as well as plants to the side of the tank, their stems/roots growing below the water line, foliage above the water surface, Pathos, Peace Lily, Swedish Ivy to name three. The plants can help maintain lower Nitrate levels, especially helpful if your tank lighting is too low to support aquatic plants that grow and survive completely submerged. The stems of plants growing in these suction cups can eventually outgrow the space allowed by the suction cup holder, so you have to keep an eye on that. Some plants will grow roots above the dying stem below, others cannot or will not do that and will eventually die. After being in the water, the suction cups will need a thorough cleaning in order to stay supple and able to stick to the side of the tank again. With proper care, they can last and adhere for a very long time.

These are really handy to keep your airstones or any other tubing in place. Easy to take apart and pop back together when it's time to do your cleaning.

Exactly what we wanted! Exactly like the picture!

These work about 85% of the time. In some spots I have to use 2 side by side to keep the air hoses where I want them