Is my filter system inadequate?

[justinhill]

...or am I doing something else wrong?

My nominally 120 litre tank, with about 84 Litres in it, came with an Oase Bioplus Thermo 200 filter system. My tank is cycled and my water is clear. I've been changing about 30% - 40% of the water weekly. After I've rinsed out the filter sponges I have good water circulation, judging by the the ripples at the surface and the swaying of all the plants. However, within a few days the pump output drops to the point where there's very little flow. So I rinse the filter out again, and flow returns to normal for another few days.

I shouldn't have to do this, surely? I'm not overstocked, all my water chemistry looks good and my water looks clear.

The filter system comprises three large sponges and one small, finer, one just under the pump inlet itself. It seems to be this small sponge that gets really clogged up. I was rinsing the filters when I changed the water; now I'm doing it every 3 days to maintain pump performance, which is boring...

 

[Dajuyu]

...or am I doing something else wrong?

My nominally 120 litre tank, with about 84 Litres in it, came with an Oase Bioplus Thermo 200 filter system. My tank is cycled and my water is clear. I've been changing about 30% - 40% of the water weekly. After I've rinsed out the filter sponges I have good water circulation, judging by the the ripples at the surface and the swaying of all the plants. However, within a few days the pump output drops to the point where there's very little flow. So I rinse the filter out again, and flow returns to normal for another few days.

I shouldn't have to do this, surely? I'm not overstocked, all my water chemistry looks good and my water looks clear.

The filter system comprises three large sponges and one small, finer, one just under the pump inlet itself. It seems to be this small sponge that gets really clogged up. I was rinsing the filters when I changed the water; now I'm doing it every 3 days to maintain pump performance, which is boring...

Kinda of hard to tell ... might help dearly if you can post pictures on your filter and tank for that matter.

 

[justinhill]

Kinda of hard to tell ... might help dearly if you can post pictures on your filter and tank for that matter.

You're right of course - I've posted so many pictures in other threads about this tank I forget that I need to put more up! It looks a bit brown in the second picture only because I removed the foil background sheet and the wall behind the tank happens to be painted brown. Also, only the rear light is on at the moment.

 

[Stanster59]

Just had a look at the filter design, Im assuming the water gets pulled in the bottom?

Sponges should go, coarse, medium,fine and then filter floss.
If the floss is getting clogged the other sponges arent doing their job,
Is water leaking in somnewhere else ?

 

[justinhill]

Just had a look at the filter design, Im assuming the water gets pulled in the bottom?

Sponges should go, coarse, medium,fine and then filter floss.
If the floss is getting clogged the other sponges arent doing their job,
Is water leaking in somnewhere else ?

There are three 'modules', each containing an identical piece of blue foam. Each module has slots in the side so water comes in both from there and from the module below it. Then at the top there is a small, denser, piece of blue foam that's right under the pump inlet. It's not a great design because as I say water can be drawn in to the top module directly as well as via the two below it. Also, it's made so that the filter 'stack' attaches to the pump and backplate magnetically so there's not what you'd call a proper seal there. I don't think there's anything wrong with the unit itself or how I've assembled it.

It is the little pump inlet filter that gets really stuffed and in principle this is the only filter that all the water must flow through and can't get bypassed. Logically, I would think that the more the lower sponges clog up, the more water bypasses to the next level up and so on. Perhaps it's meant to be that way.

Upgrading to an external filter system like a Fluval 207 would be £100 or so, which is a depressing thought but maybe that's the route to follow. It would certainly be more robust, and allow me to use different media than just blue sponges...

 

[Slaphppy7]

Why only 84L in a 120L tank?

 

[Stanster59]

I

There are three 'modules', each containing an identical piece of blue foam. Each module has slots in the side so water comes in both from there and from the module below it. Then at the top there is a small, denser, piece of blue foam that's right under the pump inlet. It's not a great design because as I say water can be drawn in to the top module directly as well as via the two below it. Also, it's made so that the filter 'stack' attaches to the pump and backplate magnetically so there's not what you'd call a proper seal there. I don't think there's anything wrong with the unit itself or how I've assembled it.

It is the little pump inlet filter that gets really stuffed and in principle this is the only filter that all the water must flow through and can't get bypassed. Logically, I would think that the more the lower sponges clog up, the more water bypasses to the next level up and so on. Perhaps it's meant to be that way.

Upgrading to an external filter system like a Fluval 207 would be £100 or so, which is a depressing thought but maybe that's the route to follow. It would certainly be more robust, and allow me to use different media than just blue sponges.I'd

 

[Stanster59]

Sounds like a really crap design.

 

[justinhill]

Why only 84L in a 120L tank?

You may well ask... So, the tank is sold as "125 litre" - first off, this corresponds to the maximum external dimensions, not the internal dimensions. Then, the included lighting system hangs down 7cm below the top of the tank, which limits the maximum height of the water.

Once you've taken all this and the substrate into account, it adds up to 84 litres. And that's without deducting for the filter unit, the bogwood and so forth. Maybe I should forget all this and just say I have a 125L tank, but I'm too pedantic for that.

 

[Slaphppy7]

LOL, understood....

Built-in lighting that hangs INSIDE the tank? Haven't seen that before....

 

[justinhill]

LOL, understood....

Built-in lighting that hangs INSIDE the tank? Haven't seen that before....

quite...

 

[Slaphppy7]

quite...

Interesting...is the fixture removable?
Sorry to digress from your original query...

 

[justinhill]

Interesting...is the fixture removable?
Sorry to digress from your original query...

Your digression is entirely welcome - although I did have a similar thread going which was related to this. The whole thing is removable but the problem is the opaque lids, which fit inside the tank - you can just make out the end of one of the rails in the top left of that picture - and sit only millimetres above the light fixture.

I have recently ordered a piece of 5mm 'glass effect acrylic' which is oversize and will just sit on top of the tank so I can discard the existing lids. This will allow me to raise the lights by putting wedges under the supports, or even replace them altogether (I was thinking about a Fluval Aquasky but I can't afford this at the moment).

I didn't choose this tank, I 'inherited' it, and I don't think much of the thing. And that brings me back to the filter unit, which I don't think works very well...

 

[Slaphppy7]

What is the length of the tank?

 

[justinhill]

What is the length of the tank?

68cm internal