# One big filter or two smaller combined?



## Aristotelis (28 Apr 2015)

I was wondering, trying to achieve the 10x flow in a 200-300litres tank, is it better to use 1 big high flow filter, or combine two smaller ones if the tank space allows of course?

Thank you in advance for any replies and sorry if the question has already been answered, I wasn't capable of finding it with search.


----------



## Tim Harrison (28 Apr 2015)

I guess it's a balancing act between minimal equipment in the tank and keeping that all important flow and distribution...most tho' seem to have two outflows and inflows in that size tank...but I suppose the type of layout and its obstructions to flow also play a part. But there are other ways to create flow such as power heads etc.


----------



## Rahms (29 Apr 2015)

If you're injecting CO2 its easier to do with one large filter and a spraybar, but two filters provides redundancy, and you can always buy a T-piece and extra needle valve for your CO2. I think either way you'll be able to make it work, but if the cost isn't prohibitive I'd go for a single whopper with a spraybar (but I have a feeling the cost _is_ prohibitive).


----------



## allan angus (29 Apr 2015)

i have gone with 2 makes cleaning the filters easter i do alternate ones each month and means if there is a problem with one the other takes some of the load ( just my opinion ) works for me ohh and if one busts replacement is cheaper


----------



## Alexander (29 Apr 2015)

2 is good when you service one and another one keeps running thus nitrification rate is not falling down.


----------



## ian_m (29 Apr 2015)

If using two filters you will need a CO2 setup as below.


----------



## Jose (29 Apr 2015)

If you are going to inject co2 via it then I would go for the biggest one you can afford. As ian shows you can do with two but its more pieces to buy and more possible leachs etc. Kepp all that in mind and compare to the price of the filter.


----------



## papa_c (29 Apr 2015)

I've gone the route as per Ian's drawing. My thoughts were it would be easier to get a consistent flow across a short spray bar. My tank length is 100cm and as spray bars that are included with a pump are never this long it would mean extension pieces required. So the options are 2 short balanced spray bars or an extended long one with possible pressure drop off. Whether this theory is correct I'm not sure but it seems to work well with two....


----------



## Aristotelis (30 Apr 2015)

Thank you all for your replies. 
I forgot to specify that I'm researching for a future low tech tank (no CO2) probably shallow tank too. So judging from your replies, maybe 2 filters might be a better solution


----------



## mattyc (30 Apr 2015)

I did run two on my tank ( before buying big eheim filter) with two it is easier to ensure that there is flow on the direction you want and that there is flow all round the tank. I still use a power head to remove dead spots.


----------



## Jose (1 May 2015)

People are getting the idea that two is better than one here. In engineering (and this is the same here), you have to keep it as simple as possible. One filter is the simplest idea. It will be half the maintainence time, half the number of pieces to put together, half the possible problems with your co2 if you inject co2 via both of them. Basically double the possibilities of things to go wrong.
What are the beneffits of two? I cant think of any really, well maybe if one breaks youd still have a small back up. But price in the the end matches up. Flow? In the end you need flow to add up and go in the same direction dont you? So its the same as using one filter. You can have the same flow using whichever method of the two.

Unless it was a really big tank. In this case youd need too big a filter to be viable. For a 300 litre its in the limit for me maybe. You can try to sum up all the money youd spend in doing something like Ians installation and compare it to buying one bigger filter. Now we are talking Maths. This way its not about opinion any more. Even if its more or less the same price you should looks at the pros and cons mentioned before.


----------



## Rahms (1 May 2015)

^ he said he's not using CO2


----------



## Jose (1 May 2015)

Rahms said:


> ^ he said he's not using CO2



My answer was more to everyone drawing the conclusion of two being better than one. People normally end up using co2 sooner or later. If he isnt using co2 then he probably doesnt need 10x flow etc. Just a smaller filter should be fine of course. But if he wants to get co2 eventually then he'll have to get 2xeverything.


----------



## Rahms (1 May 2015)

On the flip side, if it costs him more to get 1 single large filter and he never gets CO2, he's wasted money! The main thing to consider is the cost _now, _rather than trying to second guess his future decisions. I'd just grab whatever is cheapest and be done


----------



## Jose (1 May 2015)

Rahms said:


> On the flip side, if it costs him more to get 1 single large filter and he never gets CO2, he's wasted money! The main thing to consider is the cost now, rather than trying to second guess his future decisions. I'd just grab whatever is cheapest and be done



Are two smaller ones cheaper than a bigger one? I guess that depends but havent looked at a lot of filter prices lately.

http://www.ebay.co.uk/itm/All-Pond-...t=LH_DefaultDomain_3&var=&hash=item2edd6ddb30
This link for exmplae shows:
1000l/h =£50
2000l/h=£70

So I tend to think that one double the size should be cheaper than 2 half the size.


----------



## Rahms (1 May 2015)

Fair enough I'm not advocating either way, just saying cost is king and the rest is noise. After looking around, if he wants something bigger than that there aren't many options anyway


----------



## ian_m (1 May 2015)

Remember you might be able to fit in neatly and easily plumb in two 1500l/hr filters eg JBL1500's in the cabinet under the tank, whereas a single  FX6 (3500l/hr) is a monster sized bucket with extremely large non standard outlet hoses.


----------



## papa_c (2 May 2015)

Interesting about 2 vs 1 in the engineering space.... If 1 is better than two why do jets have 2+ engines? If one goes off line you can still maintain flight..... Call me over cautious but that was part of the reason I went for 2. Also my intakes are on the opposite side from the return so I get a good churn on the tank contents. Filter 1 intake is on the left side and output to the right half and vice versa for filter 2.
Sent from my Lumia 1520 using Tapatalk


----------



## allan angus (3 May 2015)

papa_cee said:


> Interesting about 2 vs 1 in the engineering space.... If 1 is better than two why do jets have 2+ engines? If one goes off line you can still maintain flight..... Call me over cautious but that was part of the reason I went for 2. Also my intakes are on the opposite side from the return so I get a good churn on the tank contents. Filter 1 intake is on the left side and output to the right half and vice versa for filter 2.
> Sent from my Lumia 1520 using Tapatalk


i agree the thing is each filter has the same number of parts (give or take a little  ) so each filter has the same life expectancy if estimated on number of component parts so lets say each has 1000 hrs average life expectancy for example. this life expectancy is not affected by using multiple filters on average its the same for each filter !


----------

