Robot for Fiberglass Pool (Dolphin M4? Polaris 9550 Sport?)


Bronze Supporter
Dec 19, 2016
Raleigh, NC
Hi All! We are entering season 3 with our fiberglass pool. We have manually brushed and vacuumed the first two seasons, but I am seriously considering a robot for the upcoming pool season. My concern is whether it will really be worth it in our situation. We have a fairly large pool in the fiberglass world - 16x37 freeform shape, with 8 bucket seats (plus the safety ledge). Key West by Tallman I am guessing the bucket seats are a lost cause and will just need to be brushed first, but can a robot get the safety ledge relatively clean or will it make the robot fall down? Our pool builder sells the M4 and that is what they suggest....but the price is awfully steep. I've heard good things about the Polaris 9550. Any recommendations? Should I just keep going with the manual vacuum/brush? Any suggestions are welcome! :)


Gold Supporter
TFP Guide
Jun 7, 2017
Damascus, MD
A robot for sure is a good choice. My 9650iQ is great it never gets stuck and is able to get onto the sundeck to clean it. It did manage to flip itself over once where I had to rescue it but for the most part is able to right itself in almost any circumstances. I am not sure what the seats are but I suspect it could navigate them just fine. Bear in mind this is the only robot I have ever known so this is just a review of the Polaris, not a comparison with other robots.

Costas > DownUnder

Bronze Supporter
Dec 17, 2017
Adelaide | Australia
How wide is the safety ledge?

My M500 had trouble climbing over mine during the colder months - however I did add some small bits of polystyrene foam to the m500 which provided additional bouyancy which did the trick.

As the water warmed up during summer though - I had removed the foam as the m500 then became too bouyant (would not sit/clean the floor correctly) but would still climb up over the safety ledge without issue.

Another thing to be mindful is that the robot will climb fibreglass walls much easier when fitted with the full width foam rollers - see my video.



Silver Supporter
Jul 29, 2018
Katy, Texas
Check out some YouTube videos. I've seen a pretty comprehensive one on the Premier and a somewhat less informative one on the M500. I decided on the M500 from Marina Pool & Spa. The M400 and M500 both have a counterrotating third brush, which has potential to clean pool surfaces better than the front and back alone. Along with some other Maytronics models, the "exhaust" water shoots straight up, which I believe helps keep the cleaner pressed to the surface of the floor or walls. The split front and rear drive system allows a "zero turn radius", which makes it pretty nimble. With the handle/floats properly configured, it also does a remarkable job at the waterline, although I take five minutes before running the M500 with a pool brush giving that problem area a quick brushing. Marina Pool & Spa has extraordinary prices, availability, and shipping. I had decided on the M400, as the M500 benefits over the M400 seemed unnecessary, at least to me. However, Marina's M500 price sold me on that one. I'm sure other less pricey Maytronics cleaners would do as well, but I've gotten into trouble too many times by trying to save a couple which my wife will attest. Getting the "top of the line" also assured that my wife would be happy with the purchase.

One downside I've found--which may apply to other Maytronics devices--the Bluetooth remote and iPhone app combine to create an exceptionally mediocre remote control system. I have to hold the iPhone almost touching the M500 for an initial connection (every time), and have to be next to the pool for it to maintain its connection. The controls are clunky and non-intuitive. All in all, the Bluetooth remote and app are nearly useless. I just plug it in and press the go button on the power supply. When it finishes, I take it out and dump the two debris collectors. BTW, this monster is heavy, especially if your water line is far below the surface. And contrary to one person who posted here, I have no debris at all run out the bottom when taking the M500 out of the pool. There are vinyl boots at the collection slots that flop over and close the opening when out of the water (see pic)M500Boot.jpg, and for me they work well--even the first couple times I used it after having a terrible pressure side cleaner previously. The dirt, tiny pebbles, and just plain muck that came out of those collectors was really disgusting. After 6 or 8 cleanings, though, it's much less but never empty. And it's frankly amazing to see it climb the pool wall and actually stick the front brush above the waterline, seemingly defying gravity.


Well-known member
Aug 19, 2013
Having owned both float-handle (albeit older) and water-directed robots, I'm partial to the newer ones with the waterjet. The handle models clean well but are limited to filter cartridges due to their design. In my experience the waterjet models clean just as effectively but have a more versatile basket design and they hold themselves against the pool walls really well with water pressure from the top of the unit (which is effectively the "back" of the climbing unit). They also shimmy sideways along the tile line using lateral water pressure. The ones without handles also weigh considerably less.


Mar 21, 2012
I live in Lake Havasu City, AZ. Can I leave these things in my pool during the summer, or do I have to have someone launch and retrieve it when I’m away?