TOPNCN 25cm Aquarium Air Stone Disc - Round Bubble Diffuser Ring for Fish Tank, Pond Oxygenation & Aeration - Durable Bubble Stone for Freshwater & Saltwater Aquariums (Perfect for Betta Tanks, Hydroponics & Turtle Habitats)

I took a chance buying these. They had very few reviews and one guy said they stopped working after 2 weeks… I hope this helps anybody that’s been searching like I have.I needed something for a hydroponic DWC twin 10 gallon setup I was building. I had a 40lpm air pump on an (8mm or 3/8”) air hose split connected to 2 - 8” vivosun airstone discs. I have had a long battle trying to find consistent quality in airstones for years. Those air stones often were lopsided or uneven and larger bubbles that weren’t properly aerating the nutrients and disturbing the roots while giving a rougher side flow.Let me say that $28 for a 9.5” diameter porous hose on a stainless weighted ring with welded loops and an 8mm brass inlet seemed like their had to be a catch, that’s a fair price in comparison. Plastic air-stones that easily break are more than this at this size. No there wasn’t a catch, these are very high quality. And if the hose ever clogs or breaks you can actually buy just the replacement hose for $16 in 25ft lengths giving you multiple replacements if ever needed. I don’t see how it’s possible they could stop producing air in two weeks without an air pump issue or flow imbalance, (more on this later) - These rings and fittings will last years, you can tell it’s quality and not surface coated.The bubbles they produce are nano to medium at full air volume from the 40l pump split to 2 of these rings in 3/8”ID tubing. They create a calm center for the roots with outside air flowing in and cycling water in almost a convection like flow - up the outside and back down the center with oxygen. Just perfect for my setup. My plants reacted accordingly.More on airflow imbalance previously mentioned- if you have a splitter off a single pump these should be hooked up fully and they should be turned on after. If you connect a different airstone to the other outlet these will not work the same as the air creates small openings in the rubber pore and the initial burst is where they continue to go through. If you hook a denser airstone up to the second line all the air will come from this diffuser ring because it has less resistance but still produces smaller more gentle bubbles. Also they need to be balanced even when using 2 identical diffuser rings. For example I have a control valve on both my airlines. If I turn one on full with the other valve closed and then open that other valve the newly opened air line diffuser ring will produce lower bubbles than the one that had the higher flow while it was closed. They need to be opened simultaneously for balance. I’m not exactly sure the physics off this so it’s anecdotal but seems to be the case.They will have some small sandy grits that come off the hoses at first. I recommend washing them and running them in a spare reservoir first to get that out before introducing to plants.Finally, id like to thank whoever the seller/designer is here. It’s been a long search and you happened to make exactly what I was looking for. I’ve searched every hydroponic shop I could find and this is the best option for DWC setups I’ve ever come across. The quality is outstanding.