Review on 🐠 Petzilla Magnetic Aquarium Glass Cleaner: Ultimate Algae Scraper for Fish Tanks, Effortless Cleaning with Floating Brush Scrubber Magnet, Scratch-Free & Non-Slip by Ashley Taylor

I ordered the smallest of these cleaning magnets for use in a 5 gallon and a 20 gallon tank. Some sell them as "small" (mini, small, medium, large). Others sell the exact same size as "medium" (small, medium, large, extra large). In any case, I had a 3.74 inch version for a 16-30 gallon tank as shown in the chart. I've had other magnetic algae cleaners before and the magnets weren't very strong and the inside came off easily. If you encounter dense seaweed (freshwater), move too fast or move around corners from one pane of glass to the next. Not so with these! The magnets are terribly strong! When I took them out of the box I had to use a lot of force to separate them because I thought the velcros were stuck together. It wasn't like that. It was the magnets themselves that created a very, very strong hold. So strong that I was afraid. Just smack the inner part into the water and pull the outer part against the glass of my 5 gallon aquarium. Without exaggerating I think if I did it like this it would easily break the glass, the attraction is so strong that I assume they use neodymium magnets inside as the attraction seems stronger than any alnico, ceramic or ferrite magnets I've used for their size and yes I know magnets. I had to attach the first magnet to the inside of the glass and then carefully attach the outer magnet to it. In a 5 gallon tank (about 1/8" glass) it's absolutely impossible to lose the internal magnet. I don't care how fast you clean or how thick your algae is. It just won't happen. I Haven't tried them in my 20 gallon tank as it's not currently set up but again I'd hesitate to just let the inner magnet smack the glass to connect to the outer The draw is awful! After cleaning, the inside of the velcro became lightly algae.A few swipes left to right and the jar was empty and I haven't cleaned the jar in months in this heavily planted and overly lit super overgrown tank.I have the smallest size Tried this product so I can't compare how well it sticks or how well it cleans, but for a 5 gallon tank with 1/8" glass this product is too effective and I was concerned about it getting through this Sticking together thin glass and the effort required to get these things working may mean that I might actually have trouble fitting the glass side to side and eventually loosening the silicone gasket in the corners of the tank. I'm not exaggerating at all. Compared to fallen apart mag float magnets, there's no question how much better they clean up! Now hopefully they last as long as the mag floats. If they don't they get a lot cheaper and I'll just buy another set if they don't fall apart in a year or so. But for a 5 gallon tank I would recommend the smallest of the sizes. Additionally, there are many sellers selling the same product on Revain under different brand names and at wildly different prices for the same product. At the time of purchase, this seller was about a dollar less ($8.49) than everyone else, with free Prime shipping. Update: It is now May 2021. The magnets have been submerged in the tank for several years. Everything is as good today as it was in 2018. The magnets are still as strong as they were. The Velcro on both pieces is still fully attached and will not come off. My glass is still not scratched. I still stand by my original rating. These are the best algae remover magnets I have ever used and I have used several different designs over the past 50+ years of using these devices. They work well and keep going. I have a limitation. I used a pair (one side black the other green) many years ago, I had two blades that lay on the glass and they worked slightly better than this. The problem with this, however, was that the razor blades quickly rusted and became serrated, and continued to leave traces of algae even where the rust spots no longer made contact with the glass. They also rusted when left outside the tank. If they could solve the rust problem, they could outperform them as the best. But I can't fault these current Velcro models as they work well and last for years!