I got curious about the use of electrolytic oxygen generators from this thread discussing the O2 Grow dissolved oxygen emitters. However, there is little to no unbiased (non-shill) reviews about the product available. https://www.rollitup.org/t/o2grow-emitters-better-than-just-regular-air-stones.863356/page-2 http://www.o2grow.com/ I'm interested in trying out this technology, but frankly the cost is far too high for me to justify that kind of spending without any proof of efficacy (aside from a few company funded studies) or analysis on the safety of byproducts that the system may produce. Additionally, I don't anticipate the cost will drop on the system anytime soon because the company has numerous patents preventing competitors from entering the market. I'm familiar enough with HHO generators to recognize that this design isn't particularly complicated from an engineering standpoint. Because of this, I thought I would share a DIY friendly design that should accomplish the same results as the O2 Grow system, while not breaking the bank. Design Principle The O2 Grow system operates by electrolysis of water. This process, in short, is the decomposition of water (H2O), by electrical current, into oxygen gas (O2) and hydrogen gas (H2). In practice, electrolysis is as simple as applying DC voltage across an anode (positive) and cathode (negative) submerged within the water 2H2O → 2H2↑(-cathode) + O2↑(+anode). The volume of gas produced by this process is 2:1 hydrogen to oxygen. https://en.wikipedia.org/wiki/Electrolysis_of_water Although the principal of electrolysis has been known about for over 200 years, there are some challenges when it comes to putting the principle into practice. The biggest challenge is corrosion of the electrodes. For example, steel, stainless steel, copper, and aluminum electrodes will all corrode relatively quickly. Hook up these metals to a 9v battery in a cup of water overnight; You'll come back to find some nasty stuff. Now imagine how much worse that would be in a salt-laden nutrient solution. In order to combat corrosion, proper selection of the anode and cathode materials is essential if you want to avoid regularly replacing them. The most common materials include titanium scaffolds in conjunction with mixed metal oxide (MMO) and platinum coatings. The anode is particularly susceptible to corrosion and so it is more important for it to have the MMO or platinum coating. Once corrosion is accounted for, the rest of the design is relatively simple. You properly space the anode and cathode and then apply a DC power source to them. My DIY Design Parts... 1. MMO Titanium Mesh Anode - $15 http://store.theamateurchemist.com/mmo-mesh-anode-2-x-6/ 2. Titanium Mesh Cathode- $10 http://www.ebay.com/itm/Titanium-Me...214757?hash=item33adbd9465:g:L2QAAOSw8-tWYBYD 3. Mean Well LPC-60-1400 (may be overkill) - $15 http://www.mouser.com/search/Produc..._campaign=709-LPC60-1400&utm_term=LPC-60-1400 4. Spacer for anode/cathode and various parts for enclosure- $5-10 Total: ~$50 I have access to a 3D printer, so I'm planning on printing an enclosure and spacer for the emitter. The space between the anode and cathode should be about 1-2 mm. You could use some nylon washers to get the distance right. Just make sure the anode and cathode are not in contact with each other. Here are some images of the cad model that I'm planning to print up... Upcoming Work At the moment this is just a concept. I've done some tests with the anode and cathode and have confirmed that the materials I specified are corrosion resistant. My primary goal right now is to do some testing with various DC voltages and current sources in order to optimize HHO generation rates while keeping heat generation down and minimizing the voltage. Whether or not this method will impact our yields is up for debate. I'm willing to give it a try and will update you with my findings. To be honest, I'm skeptical that HHO generators will prove to produce superior results to traditional air stones. However, I like to tinker and that in and of itself is worth giving it a shot. Obligatory Disclaimer Safety is paramount when working with electricity and water. These voltages and currents can potentially kill you. Use proper precautions.