Prefilter - really external

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safcraft

Registered Member
Jun 30, 2020
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Hi,

I wanted to ask a question to you experts here, regarding filtration.
I am putting up a new 500L tank ( returning to the hobby again after 20 years!) and have an EHEIM 3e 700 ready to use.
I want to use add an external pre-filter to this, really external, not the sponges you attach to the inlet pipe inside the aquarium.

Can i use an old Classic EHEIM filter with nothing but coarse foam inside as a pre-filter ?
Classic line usually has a 12/16mm inlets and my Prof 3e has 16/22mm hoses.
Will the Prof3e be working too hard to suck the water out of the aquarium through the Classic pre filter ?

What about sometthing lke this ? It is cheap but also has 12/16 inlet pipes.

61KOgcjOe6L._AC_SL1024_.jpg

Suggestions?
Thanks a lot
Filipe
 

dougall

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Mar 29, 2005
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Why would you want another filter inine with the other?

I normally use a screen or such over the filter intake to stop fry or such going into the filter. Otherwise I wouldn't be worried, having media in more than one location seems to be more to clean

I think it should work, but I wouldn't, I'm not going to look up numbers but a bigger hose allows faster water flow. Changing the size of hose used in the filtration system is really just going to add another potential point of failure.
 

safcraft

Registered Member
Jun 30, 2020
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Goal is have coarse mechanical filtration before the main biological filter. Thats what a pre filter does and it seems you use it too with your screen.
I can clean and do maintenance on this prefilter every couple of weeks to clean debris, and leave the biological filter alone for months.

I dont want to use the sponge filters inside the tank on the inlet tube, as i dont want to keep opening the tank (it will be closed and covered).
It is easier for me, to open the bottom cabinet, take the "prefilter" out and clean it in 2 minutes (as its a pre-filter i can use tap water to clean it).
 
Apr 2, 2002
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New York
About the easiest way to break and pump or filter is to impede the intake side. If one wished to slow flow and there is no flow control on the device involved, the way to reduce flow is to limit the return/outflow side. This has the same effect as increasing the head.

A pre-filter is intended to prevent larger particles from entering the filter. Pre-filters need to be rinsed regularly because clogging them, surprise, surprise impedes the intake.

I use the ATI Filter-Max #3 prefilters on my three running Eheims and even on an AquaClear 500. I also use them on some powerheads.
https://kensfish.com/products/ati-filter-max-3-pre-filter?_pos=1&_sid=9c344db12&_ss=r
 

dougall

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Mar 29, 2005
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The only reason I have a screen or foam in the tank as a prefilter to keep fry or shrimplets out if the filter.

Otherwise I would add your sponges to the canister, before the biological media.

I gave also never had a problem rinsing filter media under chlorinated tap water. No cycle crashes or anything.

Best thing it seems you can do is just to go for it. It may be just fine.
 

fishorama

AC Members
Jun 28, 2006
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SF Bay area, CA
I use sponge prefilters like TTA or a DIY equivalent. If I were to have a second filter I would use it separately to increase overall filtration & flow. I use 2 filters on almost all tanks 20g & up. For small tanks I have used the "skinny" sponges that some filters use (I think it's a Fluval they're made to fit). Mostly those would be for much smaller tanks than yours.

There are small screens like dougall uses, it keep some big debris & animals out but not maybe not as well as big sponges do. Either should help but I haven't used them. Both will need regular cleaning every week or 2.

I find canister filters a PITA to clean but they only need that every several months...with something to keep out big "crap" like leaves, & critters. I can't see the advantage of having 2 canisters in series, it won't reduce maintenance on that first 1...

Is it the aesthetics of sponge prefilter you don't like? A 5 minute sponge rinse & squeeze under running tap water every 2 weeks is much faster than cleaning a canister...& a black prefilter sponge with a black tank background & you almost can't see them...

What kind of tank is it? Planted? Big cichlids? That can make a difference too...
 
Apr 2, 2002
2,348
127
66
New York
I find canister filters a PITA to clean but they only need that every several months
I had always cleaned my two Eheim Pro II 2036 canisters twice a year- June/Dec. But when I set up my thrid I had begun working with Poret foam- both the cuves and the Mattenfilters. So I asked Dr. Tanner what he thought about Poret in a canister. He said I should try it and that I should not use any other media beside the Poret. No floss and no Eheim media. So i loaded up both baskets with 20 ppi foam. It occurred to me that Dr. Tanner suggested that I did not need to clean my Mattenfilters until the water level behind the foam was lower than the level in the tank.

So I asked him when I should clean the foam in the canister and he said, "when you can see that the output has slowed from when you started it up. That took over 3 years. I will admit that it is on a planted 75 which also has an AC 300 gph on it that gets cleaned weekly (for the most part).

Also, I clean the Eheims, from turning it off to turning it back on, in about 40 minutes. That averages out to less than 2 minutes a week. How many filters can one clean in 2 minutes?
 

dougall

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Mar 29, 2005
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I would have to side with Dr. Tanner here too. I can see no reason to have an extra chamber for more media.

But I'm always cool if people want to overcomplicate the setup if they really want. I would invest in something to monitor potential leaks though.
 

fishorama

AC Members
Jun 28, 2006
9,958
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144
SF Bay area, CA
I'll have to look at the different Poret-type foams, some are more dense & would clog fast even with a prefilter. I have a block of fairly fine foam I was given, I don't know if it's Poret or not. & also a coarse sheet, not really foam, more fiber-y...but like I think of some Mattenfilters. I don't think that would clog for a really long time...with a prefilter.

Yes, TTA, that's about how often I clean my canisters. But I do wait until the return flow slows, might be 4 months or maybe 8+, it depends on the tank.

I "can" clean a canister in 30 minutes...if everything goes according to plan...it sometimes doesn't.
 
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