I've been using the Zelerdo feeding rings for about a month now in my 20-gallon community tank. At first glance, they seemed like a perfect solution to contain my fish's flake food mess.

The square design is clever - it creates clear boundaries that even my greedy tetras respect. I particularly like how the inner space (about 3 inches) keeps food concentrated while allowing fish to swim through freely. No more watching flakes get sucked into the filter!

However, the suction cups are hit or miss. Two sticks reliably to my tank wall, one needs daily reattachment, and the fourth gave up entirely after a week. I've found they work best on completely dry glass - any algae film and they're useless.

Durability is decent for the price. The rubber material hasn't degraded in my water parameters (pH 7.2), though I did notice slight discoloration after prolonged use. They're surprisingly easy to clean - a quick scrub removes any biofilm buildup.

One unexpected benefit? They make great temporary plant corrals! I've successfully used them to contain floating hornwort while my other plants establish. Just don't leave plants in them long-term - I noticed reduced surface gas exchange when using all four rings simultaneously.

For basic feeding purposes at this price point, they're functional if you manage expectations about suction reliability. I wouldn't trust them for critical applications, but as simple food containment? They get the job done with minimal fuss.