I have had great experiences with this product on glass aquariums and miserable experience using it on acryllic. We have even used the metal attachment blade on Starphire glass (which is a bit softer) with no issues. If you have glass, you need not read the following as it won't apply to you. You MUST ONLY use the short blades on acryllic. The longer blade is 30% fiberglass and will scratch acryllic. Just my .02 here: This information is listed in the instruction manual - but buried on page 17. I did not think that I would have to read 17 pages of instructions to learn such a valuable tidbit after using magnets professionally for 18 years and I am really miffed at Tunze for not being more forthcoming about this information. There website appeared to be promptly changed after I logged my complaint with the US distributer. I'm told the newer product manuals have also been edited, but I have not seen the reprint yet.
The second issue I have with this product is that the outside piece is kept off of the surface by 4 relatively thick felt pads, similar to what you put under chair legs to prevent scratching the floor. First, the glue lets go with any moisture and the pads will travel. Second, and more important is the gap that forms allows any metal flecks that may be around to get picked up by the magnet. The gap allows the particle to travel into the felt pads. We had an incident where we inspected the magnets prior to use and they were clean. We cleaned the first panel on a tank without incident, even knocking out some coraline algae at the sandbed quite nicely. There must have been some bits of metal between the cabinet trim and the aquarium, because the second side of one tank started to scratch on the outside. Upon inspection, we found bits of metal imbedded in the felt pads. They were not visible to the naked eye and we only found them by running our fingers over the felt. We have remedied this information by replacing the felt pads with "standard" stick on felt like is used on Magfloat or Magnivore products. Now, there is no room for bits to get under the surface, unless it is used on a curved aquarium. We still find that due to the very slender housing, it will attract any metal bits that are sufficiently close, but with our modified felt, they cannot get under the outside surface now.
My last gripe about these is the cost of blades. Replacements are about $5-6 per set wholesale and we are only getting about 10 uses out of each set. Granted, we are using them to attack some coraline that traditional acryllic tools would not touch and they are seeing extra wear as a result. If your acryllic is not already compromised with coraline, this could be a good tool for you. All of the acryllic tanks we work with are 8-25 years old though and they have age appropriate growth and wear. Many have purple picture frames on the edges where older tools would not reach. I'm hoping that as we clean these edges out, we will get better life out of the blades.
Having said all of that and working out the flaws, these things are fantastic on tall, flat panels. We have a couple tanks that are 48" high with mature SPS growth, so the bottom edge is a nightmare to clean with sticks and magnets don't reach beyond the bottom trim. For these aquariums, the product is exceptionally useful.
Webmanny, please take these comments to heart, especially if you are used to working with conventional flat surfaced magnets. This product could be a real labor saver for you, but take these experiences into account and use it with care. Only operate them in a horizontal motion on curved surfaces. There are some very positive attributes to these magnets, but also some serious considerations if they are being used on acryllic.
