I am reviewing the Marina Slim S10 HOB filter for my 10 gallon aquarium
Mine has slots for 2 filter cartridges, but they make the S15 with 3 slot, and the S20 with 4 slots for those size aquariums, as well.
I purchased mine on Amazon.com at this link.
Amazon Marina Slim S10
Summary
I set up a 10 gallon aquarium last month using both an undergravel filter and a HOB filter for water polishing. Decades ago I used the same setup and it works well and provides plenty of biological filtration and water polishing. After researching several brands I settled on this because it was SLIM, hence the name, got good reviews on Amazon, has the motor in the tank for both quiet operation and self-starting after a power outage, and it came with an intake tube coarse sponge cover. Water flow is plenty for a 10 gallon tank, and it is extremely quiet. Basically I love this filter! I highly recommend it for a nano tank, either a 5-10-15 gallon, although I'd likely go with an AquaClear AC30 for a 20 gallon tank. They used to make one for a 5 gallon tank but I don't see them anywhere, so it may have been discontinued, but this will work on a 5 or a 10 gallon tank.
How long have you owned this product?
I bought this on April 26, 2026, so I have had it just under a month at this point. I've modified it so have become pretty familiar with it, and I become more convinced this was a great purchase decision.
Ease of Use (if a product)
The filter is very easy to use, I got it up and running in minutes. Below are pics of my tank and the filter viewed from above, mounted and running. It worked fine right away, but after two weeks, I noticed that the filter cartridges were clogging up a bit and water was running over an overflow dam and back into the tank without going through the media. I bought some FilterFirst water polishing pad material and cut it slightly larger than the carbon cartridge insert and it fits perfectly. There are small slots the cartridges slide into, and the FilterFirst pad is a combined coarse/fine pad and the stiffer, fine side slides into the slot really snugly. As soon as I did this the flow was greatly improved and on full flow, there is not water going over the overflow dam.
I am still cycling this tank with Tetra Safestart, so I did not replace the Bio media cartridge, but after the first water change I plan on removing that, as I don't need more bio media with the UGF, I will just use two of the FilterFirst pads in place of the cartridges. One could put more coarse sponge in front of these if desired, or you could drop a media bag or Purigen bag after the polishing pads. Another modification I made is to diffuse the water flow, which was quite strong. I had purchased a sheet of 1" thick 20 PPI sponge and I cut a chunk out to fit snugly on the spillway and attached it with a rubber band. Now the flow drops through the sponge and I don't see my little guppies struggling against any kind of current now. The third photo is after replacing the one cartridge with a polishing pad and putting the flow diffuser in place.
Pros: This is a slick little filter, very SLIM, self-priming, super silent, and easily hot-rodded with pads or other media. The flow rate is adjustable through a pretty wide range.
Cons: Frankly, I cannot think of any. Cartridges, I suppose, but nobody likes those on any filter and most of us modify them with reusable media, so I can't knock this filter for that.
Conclusion: I heartily recommend this filter for any 10 gallon tank, and would recommend the S15 for a 15 gallon. I'd probably go with an AquaClear 30 for a 20 gallon, as mentioned, but this is great for the smaller tanks. I think the S10 is not overkill for a 5-gallon nano tank on the low-flow setting.
This is original setup, out of the box.
This is after replacing the left cartridge with the FilterFirst polishing pad and attaching the 20 PPI foam flow diffuser to the spillway with a thick rubber band like those that come on bunches of broccoli at the produce section.
Mine has slots for 2 filter cartridges, but they make the S15 with 3 slot, and the S20 with 4 slots for those size aquariums, as well.
I purchased mine on Amazon.com at this link.
Amazon Marina Slim S10
Summary
I set up a 10 gallon aquarium last month using both an undergravel filter and a HOB filter for water polishing. Decades ago I used the same setup and it works well and provides plenty of biological filtration and water polishing. After researching several brands I settled on this because it was SLIM, hence the name, got good reviews on Amazon, has the motor in the tank for both quiet operation and self-starting after a power outage, and it came with an intake tube coarse sponge cover. Water flow is plenty for a 10 gallon tank, and it is extremely quiet. Basically I love this filter! I highly recommend it for a nano tank, either a 5-10-15 gallon, although I'd likely go with an AquaClear AC30 for a 20 gallon tank. They used to make one for a 5 gallon tank but I don't see them anywhere, so it may have been discontinued, but this will work on a 5 or a 10 gallon tank.
How long have you owned this product?
I bought this on April 26, 2026, so I have had it just under a month at this point. I've modified it so have become pretty familiar with it, and I become more convinced this was a great purchase decision.
Ease of Use (if a product)
The filter is very easy to use, I got it up and running in minutes. Below are pics of my tank and the filter viewed from above, mounted and running. It worked fine right away, but after two weeks, I noticed that the filter cartridges were clogging up a bit and water was running over an overflow dam and back into the tank without going through the media. I bought some FilterFirst water polishing pad material and cut it slightly larger than the carbon cartridge insert and it fits perfectly. There are small slots the cartridges slide into, and the FilterFirst pad is a combined coarse/fine pad and the stiffer, fine side slides into the slot really snugly. As soon as I did this the flow was greatly improved and on full flow, there is not water going over the overflow dam.
I am still cycling this tank with Tetra Safestart, so I did not replace the Bio media cartridge, but after the first water change I plan on removing that, as I don't need more bio media with the UGF, I will just use two of the FilterFirst pads in place of the cartridges. One could put more coarse sponge in front of these if desired, or you could drop a media bag or Purigen bag after the polishing pads. Another modification I made is to diffuse the water flow, which was quite strong. I had purchased a sheet of 1" thick 20 PPI sponge and I cut a chunk out to fit snugly on the spillway and attached it with a rubber band. Now the flow drops through the sponge and I don't see my little guppies struggling against any kind of current now. The third photo is after replacing the one cartridge with a polishing pad and putting the flow diffuser in place.
Pros: This is a slick little filter, very SLIM, self-priming, super silent, and easily hot-rodded with pads or other media. The flow rate is adjustable through a pretty wide range.
Cons: Frankly, I cannot think of any. Cartridges, I suppose, but nobody likes those on any filter and most of us modify them with reusable media, so I can't knock this filter for that.
Conclusion: I heartily recommend this filter for any 10 gallon tank, and would recommend the S15 for a 15 gallon. I'd probably go with an AquaClear 30 for a 20 gallon, as mentioned, but this is great for the smaller tanks. I think the S10 is not overkill for a 5-gallon nano tank on the low-flow setting.
This is original setup, out of the box.
This is after replacing the left cartridge with the FilterFirst polishing pad and attaching the 20 PPI foam flow diffuser to the spillway with a thick rubber band like those that come on bunches of broccoli at the produce section.
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