Undergravel filtration not as good as I'd hoped...

[njparton]

I set up a 130 litre freshwater tropical fish tank about 3 months ago, and I've not yet been able to get the water as clear as I'd like.

The tank is about a metre long so I started with 2 uplifts in the back corners, with 2 air stones driven by a large powerful air pump. At the outlets I had some carbon filter attachments.

Not being satisfied with the amount of water (apparently) flowing through the filters and the noise of the air pump, I swapped one air stone for a powerhead after a month, and then the other for a second powerhead, about a month ago. Both powerheads draw in air through a venturi system to aerate the water.

The problem appears to be 2 fold:

1. the water always seems to have a slight milkiness to it. Today especially and I only changed about 25% of the water 2 days ago too!! I've tried adding a floculating agent to bind small particles together, but that's not really helped and I don't like adding too many chemicals to the water.

2. I can see very small particles being drawn up through the uplifts, through the powerheads and being injected back into the the water. The gravel covering my filter base is about 2cm thick over the entire surface, so I guess it's pretty easy for small particles to pass through the gravel? I've since read somewhere that it's advisable to add a layer of filter gloss over the undergravel filter bed before adding gravel. This (apparently) filters out small particles and creates more surface area for bacteria to grow on.


In my haste, have I set up my tank incorrectly - should I have used a layer of filter gloss? Should I endevour to add some more gravel to my tank to help remove the smaller particles?

Thanks in advance...

***Edit***

I guess I should also add that I have 4 plant, 3 from the grass family and one refered to as an "onion" plant...

The tank is lighted by 2 fluorescent tubes. The temperature is about 25-26C and I've tested for all the usual things:

Ammonia = 0
Nitrite = 0
Nitrate = 50 mg/l (and goes up surprisingly quickly)
pH = 6.5 (and sometimes drops to 6 after a few days)

 

[wetwetwet]

Hi nj,

I've never used a UG.... - I beleive externals or internals are more common and easier to maintain....(though I'm sure theres fans of UGs still)

Idk what to suggest to get the UG to trap fine particals.... but you could add additional filtration (internal/external) that could incorporate filter floss and carbon to clean/polish the water.

What are the powerheads rated at? What thickness of gravel?

 

[njparton]

Hi nj,

I've never used a UG.... - I beleive externals or internals are more common and easier to maintain....(though I'm sure theres fans of UGs still)

Idk what to suggest to get the UG to trap fine particals.... but you could add additional filtration (internal/external) that could incorporate filter floss and carbon to clean/polish the water.

What are the powerheads rated at? What thickness of gravel?

Hi, thanks for replying.

The gravel is about 2cm thick over the entire base.

The powerheads are rated at up to 126 gal/hr (470/570 litres per hour depending on whether that's imperial or US gallons!) and I have them both on a medium setting. Any higher and it looks like the water is being disturbed too much.

If I have 2 uplifts, 2 powerheads and a heater I'm not sure I have any room for an internal filter - are external filters any good?

It looks like you are in the UK? - any recommendations for an external filter?

Thanks

 

[CFC]

If your buying a external filter then look no further than the ehiem proffesional 2 range,a little expensive but IMO the best canister filters on the market.

 

[Mogo]

Agree with CFC on the Eheims. Run them on all my tanks, except for my wee 7gal, but if Eheim made them that small, I'd be right on it.

I used UGF's many, many years ago. I found they we're more of a pain than anything else, but as CFC there are probably still UGF fans out there, so this is just my opinion. I prefer external canisters.

 

[njparton]

Well I've just been out and bought a Fluval external power filter to suppliment my undergravel filtration.

I've removed one of the powerheads (guess it will become a spare) and put the intake in the centre back of the tank, about 10cms above the bottom. The outflow is where one of the powerheads used to be. I'm sure I can connect it up to use one of the uplifts as the intake....?

For now I'm going to let it all settle down and see how it goes. The filter user guide advertises some gloss "that polishes the water to a shine" and I may put some in as the last stage of filtration (filter came with a coarse foam screen > activated carbon powder in a fine mesh bag > and some white tubular stoney things for bacteria to grown on - in that order).

Anyway, fingers crossed and thanks for the replies