Eheim Filter Ratings

[Ghoti]

Hi Folks,

Been doing some reading up on filters this evening and it sure is a hot topic.

It seems that eheim have consistenly lower flow rates for any given size filter. e.g. classic 2217 & Pro 2228 are rated at 1050 lph and quote for tanks to 600l, whereas Otto PF450G (my favourite is rated at 180lph and for tanks to 600l.

Given the 3 times turnover rule of thumb the eheim seems under-rated. Then again, some say eheim rate their filters complete with media and max head height whereas others rate their filters empty. I can only find opinions on this, not facts.

Any ideas on how to compare? I'm looking at filters for a 600lt tank.

Cheers,
Scott

[ILLUSN]

this is a little like comparing apples to oranges but here we go.

eheim (as most filters) are rated at an empty flowrate with 0 head height. this means no media and water just gusjhing out the outlet.

The realworld flow rate (full of media) of an eheim 2217 or 2228 with 1m of headheight is ~600L/H

MORE FLOW DOES NOT EQUALL MORE OR BETTER FILTRATION! GET FLOW RATE OUT OF YOUR HEAD WHEN YOU ARE MEASURING FILTER CAPACITY. BIOLOGICAL FILTER CAPACITY IS DETERMAINED BY MEDIA VOLUME AND CONTACT TIME. FLOW RATE IS ONLY A MEASURE OF TURNOVER.

this means that a filter wich pushes water up from bottom to top will work better then one that goes from top to bottom, going from bottom to top forces the water to fight gravity and increases the dwell time within the filter. this gives the biomedia more of a chance to work on the water.

eheims have massive biocapacity a 2217 will hold 5.45L of bio media easy, a 2228 or 2028 5.9L, a 2080 11.8L. Its this MASSIVE capacity that gives eheims their higher rating.

a good eg of this is an eheim 2217 vs an aquaclear 110 (my favorite hang on filter best money i ever spent thats not a 2080)
2217 ~600l/h 110 1892L/H
2217 5.45L bio media 110 3L of bio media (MAX)
factory rated 600L 110 factory rated 415L

I dont use filters for mechanical filtration ( i use a sponge and a siphon), but this is one area where a higher flowrate would be benificial.

General rule of thumb divided rated capacity by 2 if your diligent by 3 if your lazy. so for a 600L tank pick a filter sized for 1200L-1800L tank.

I would only use a single 2217, 2228 or 2028 (really dont like 2028's) on a 200-300L tank, any bigger and I'd use 2 filters or go to the 2080 (good for up to a 650L)

[Ghoti]

Certainly makes sense to me ILLUSN.

And now for the $64 question....

When using 2 x 2217's for instance, would you daisy chain them increasing dwell time) or run them completely indepenently?

Cheers,
Scott

[ILLUSN]

Individually has more advantages the only real reason to use them in series if to have less plumbing in your tank ( or if your a freak like me)

[Ghoti]

MORE FLOW DOES NOT EQUALL MORE OR BETTER FILTRATION! GET FLOW RATE OUT OF YOUR HEAD WHEN YOU ARE MEASURING FILTER CAPACITY. BIOLOGICAL FILTER CAPACITY IS DETERMAINED BY MEDIA VOLUME AND CONTACT TIME. FLOW RATE IS ONLY A MEASURE OF TURNOVER.

OK - Just to prove I'm a slow learner - given two filters of the same media capacity but with 2 flow rate options (1200l/h or 1800l/h) I take it the lower flow rate will provide better biological filtration whereas the higher rate would provide better mechanical filtration.

And given the two filters in question its only $10 and the impeller that differ, would I be better off going for the best biologial filtration (i.e. the 1200l/h with longer contact time)?

The application will be discus in a 4x3x2 tank with sand substrate, DW with some peacock moss and needle leaf java fern.

Cheers,
Scott

[ILLUSN]

OK - Just to prove I'm a slow learner - given two filters of the same media capacity but with 2 flow rate options (1200l/h or 1800l/h) I take it the lower flow rate will provide better biological filtration whereas the higher rate would provide better mechanical filtration.

correct

And given the two filters in question its only $10 and the impeller that differ, would I be better off going for the best biologial filtration (i.e. the 1200l/h with longer contact time)?

The application will be discus in a 4x3x2 tank with sand substrate, DW with some peacock moss and needle leaf java fern.

Cheers,
Scott

If its only $10 in outlay and the same power consumption I'd lean towards the faster flow rate, that is assuming you have atleast 8L of biomedia which should break down the ammonia in a single pass, if the media capacity is smaller I'd go the lower flow rate to maximise contact time.

Remember a 4x2x2 is only 450L and the 1200L/h model should give you 600-900L/h of real world flow where as the 1800 will give you 900-1200L/h.for a discus tank i wouldn't want more than 3x tank turnover/ hour (so max would be 1350L/h flow) and no less then once an hour 450l/h).