Why is my hob filter overflowing on the intake?

The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.


Aquarium Advice Apprentice
Jan 7, 2022
I have this hob amtra 370 filter and i have ''upgraded'' like this,because,as it works,the water pumped up flows from the first chamber to the 2nd one and out withoyt anything in the way.Water always chooses the easiest route,therefore the top water which is unfiltered ended up going out from the out take and i modified like this.I put a plastic devider,which snugs tight in place,so the water entering the 1st chamber has to move down,into the 2nd chamber up and out.So,o put some medium foam on the intake tube,to stop some debris,then i pit a block of coarse foam in the first chamber,then some filter floss and then my bio media(weighted for the litres i have).The filter at full power overflows as you can see from the intake chamber and everything is cleaned up very well(i clean weekly).What can i do?I consider the floss essential and i ve already taken some of the bio media off...What am i doing wrong?Any suggestions?


  • 271752104_678104713367086_425660799974756450_n.jpg
    159.3 KB · Views: 98
  • 272736355_820424592681975_925982235448630912_n.jpg
    126.4 KB · Views: 80
Im not a HoB person. Can you explain the set up more so i understand it, or confirm how im seeing it?

The intake feeds the back chamber? And water flows over the top of the divide into the front chamber?

How do you want it to flow? Kind of down through the back chamber, under the divide through the floss, then up through the front chamber to the output?
Last edited:
Ive just been watching an unboxing of your filter on youtube. It looks like the filter cartridge comes in 2 pieces, a bit with all the media and filter pad and a seperate piece that can be used as a divide. It looks like you made your own divider? The divide it comes with is just an open mesh, so that should balance the water levels in the front and back chambers better than a solid piece of plastic. Cut a piece of sponge for the back, and add a bag of biomedia to the front. A photo of your filter with this set up is on their product webpage.


If im understanding how you are trying to set up your filter, pushing water down and through the filter floss at the bottom, that just isnt going to work. You need better free flow of water between the front and back chambers, either by using the divide that should have come with the filter or making a load of holes in the divider you made (if you did indeed make your divide). I think this means it wont work how you hoped, but you cant really force water where it doesnt want to go short of enclosing it completely with some kind of watertight lid, more like a canister filter.
Last edited:
I don't currently have much HOB experience, but I'm learning. I have one running on an isolation tank loaded to the brim with medium-sized sintered media only. I use a separate sponge filter that's rated for twice the tanks size as mechanical. This configuration is based on the idea of allowing bio media to run with very little restriction in a limited/low-power environment. After being seeded (with BB) this 20g kept a 2lb fish going for 3-weeks with solid water parameters.
From what i figured out,you cannot force water in those filters.They are not like canister filters or even internal ones,which are closed,and the water has to go through wherever you make it to.So i took the divider off,did a small modification,i compromised with the idea and it s a lot better now.
It's overflowing because you filter media is slowing down the flow a little, it happens with mine.
It's overflowing because you filter media is slowing down the flow a little, it happens with mine.

The same effect is present in canisters, except being under pressure makes the inevitable slowing take a lot longer. There are ways to slow clogging in an HOB/cannister but it takes a minimal understanding of how filter mats work, and the debris load generated in the tank. One thing I'm coming to accept in my HOB is that it may need to be cleaned at a moments notice to remain effective.
One easy way to extend the filter life of any HOB filter is to add a foam pre filter on the intake.
You will be be amazed about what what it filters out before is gets to the main filter.... and they are easily cleaned and can be an reused several times .
Top Bottom