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Discussion Starter · #1 ·
Ok so I have been wondering as to what a good flow rate is for internal filters for the following tanks:

a. 20 Gal Goldfish tank, 10 Goldfish inside
b. 15 Gal cichlid tank (7 yellow princes, all juvies <4 cm)
c. 15 Gal ABN pleco and shrimp tank, java moss
d. 20 Gal South American Cichlid tank, planted, el natural/dirt tank

There are several sources of information out there on the web and many of them are conflicting. Here is what I have found out so far and I would like your opinions on these.

a. 10-12x the volume of the tank
b. uncertain; values range from 6-8x the volume of tank to 10-12x the volume
c. none, filtration through sponge or corner filter suggested.
d. because it is a Walstad tank and planted, a rate of 4-5x the volume seems to be recommended, however lower flow rates do seem to work too...
 

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That's an area where there seems to be lots of really firm ideas but no consistent answer. I can't begin to fit a firm answer to fit all the different tanks that I have had/seen.
I have to fall back to looking at what works in each tank. The filter does two things for my tanks. It does mechanical cleaning to keep it looking clean. It does bio-filtering to keep the ammonia/nitrite converted. Beyond that I use cheaper, far more practical powerheads to get water movement where needed. Powerheads are easier to get where I want and muc less nuisance to clean.

A. Sounds like too much to me. Passing water through faster doesn't automatically mean it is doing a better job of bio-filtering. The high numbers may mean they are using filter flow to do what powerheads might. Goldfish may be messy but that is not a reason for me to make them stressed by too much flow just to keep debris moved out.

B. Not practical to assign a number. If you have a bad filter that holds little media does it work better than a good filter with lots of media? People sometimes assign numbers that may fit their tank without considering they may have totally different needs. People often use numbers to bypass their lack of understanding.

C. Same deal. Even if it is different fish, I still want bio and mechanical up to doing the job. A pleco might live in a hog wallow but i still have to look at it??? If a sponge does the job fine, if not I want something else. Numbers mean nothing.

D. I want enough current to move the CO2 well but not move the soil. Just can't find a number to work without knowing what is in the way or blocking flow. A tank of val make work different than a tank full of tiny grass or moss. Pick a number or ignore the numbers and fit it to what works?
 

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Discussion Starter · #3 ·
That's an area where there seems to be lots of really firm ideas but no consistent answer. I can't begin to fit a firm answer to fit all the different tanks that I have had/seen.
I have to fall back to looking at what works in each tank. The filter does two things for my tanks. It does mechanical cleaning to keep it looking clean. It does bio-filtering to keep the ammonia/nitrite converted. Beyond that I use cheaper, far more practical powerheads to get water movement where needed. Powerheads are easier to get where I want and muc less nuisance to clean.

A. Sounds like too much to me. Passing water through faster doesn't automatically mean it is doing a better job of bio-filtering. The high numbers may mean they are using filter flow to do what powerheads might. Goldfish may be messy but that is not a reason for me to make them stressed by too much flow just to keep debris moved out.

B. Not practical to assign a number. If you have a bad filter that holds little media does it work better than a good filter with lots of media? People sometimes assign numbers that may fit their tank without considering they may have totally different needs. People often use numbers to bypass their lack of understanding.

C. Same deal. Even if it is different fish, I still want bio and mechanical up to doing the job. A pleco might live in a hog wallow but i still have to look at it??? If a sponge does the job fine, if not I want something else. Numbers mean nothing.

D. I want enough current to move the CO2 well but not move the soil. Just can't find a number to work without knowing what is in the way or blocking flow. A tank of val make work different than a tank full of tiny grass or moss. Pick a number or ignore the numbers and fit it to what works?
Thank you for your insight. I appreciate your valued input (the reson why I posted in the first place! :icon_smil). Only problem is, I do not have any filters to try out what works best; I am about to order them online and won't have a chance to return the items if one doesn't meet my needs or is beyond what I need.

For A, I can just attach the filter exit (all internal filters btw) to a top &hob style DIY section that allows the water to drip back into the aquarium and loose much of the current force.

As for the others I have no way of knowing I guess at this point... Maybe buy 1 of each and then try each one out in different setups and order as necessary?
 

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One, if more expensive approach, is to order a larger filter with adjustable flow control. That way you can 'tune' each filter to a specific tank situation.

For canister filters, Eheim 2315 or Eheim 2073 would be some of the choices.

v3
 

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Sorry! First answer may have been what I thought was right but not very helpful in the real world. I might try again?
I find when totally in confusion, I can get a somewhat cloe idea from the specs put out for filters. I tend to go with a bit more than they would recommend, though. If they say good for a 20 gallon, I might feel it better suited for a ten gallon. Unless one gets in to a real whirlpool situation, having a bit more than needed is often better than too small.

Maybe something like this?
One rated for
30, 20 , 20 and 40 gallons?
Reason for me to follow gallon rating more than flow is my feelings about the media and how some are far more effective than others. Judging by flow alone, one might easily get into a setup where there is a torrent of water but not much actual filtering happening. Flow is a fine item for getting numbers that are easy but for actual needs of the "normal" tank, I find they do a better job rating the size tank it will work without excessive cleaning, etc.
What to buy can also depend on what you might expect in future tanks. Many of us do become addicted to larger!
 

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Discussion Starter · #6 ·
Sorry! First answer may have been what I thought was right but not very helpful in the real world. I might try again?
I find when totally in confusion, I can get a somewhat cloe idea from the specs put out for filters. I tend to go with a bit more than they would recommend, though. If they say good for a 20 gallon, I might feel it better suited for a ten gallon. Unless one gets in to a real whirlpool situation, having a bit more than needed is often better than too small.

Maybe something like this?
One rated for
30, 20 , 20 and 40 gallons?
Reason for me to follow gallon rating more than flow is my feelings about the media and how some are far more effective than others. Judging by flow alone, one might easily get into a setup where there is a torrent of water but not much actual filtering happening. Flow is a fine item for getting numbers that are easy but for actual needs of the "normal" tank, I find they do a better job rating the size tank it will work without excessive cleaning, etc.
What to buy can also depend on what you might expect in future tanks. Many of us do become addicted to larger!
Only problem is, the filters were not rated for volume at all :( which is why I posted the flow rates.

Also, there seems to be an idea that planted and dirt tanks even more so should have lower flow to allow bacteria to settle in the filter and do their job (nitrification) properly. Perhaps not though, from what you have told me.

If I could only select the filters :icon_neut
 
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