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Re: NFC: Filter types (VERRRRRRY LONG ... got carried away,sorry)


All the filter types work, but they all have pros & cons. 

I mostly keep killies and other small (4" and under) native fish. I have well-water that runs through a whole-house water system (resin-bed, but no salt) and comes out with low TDS (+/- "hardness") at about room temperature, which allows me the great convenience of being able to run water straight from my tap into fish tanks via a garden hose. Bear in mind that YMMV (your mileage may vary), what works for me might not work for you, given your fish/time/budget/"fish_room_practice"/etc. 

I have big canisters (Magnums) on my 55-gal and 33-L tanks in my living room. They were recommended by an experienced guy in my killie club with a similar set-up. They're relatively expensive at about $60 apiece by mail-order ... but (if you have them adjusted so there's no surface turbulence) they are ABSOLUTELY INAUDIBLE, a mandatory attribute for ensuring domestic tranquility at our primary living area. Zero water splatter. (In freshwater, I have not tried these in salt-water,) I break them down for cleaning once a month, it takes about five minutes per unit. Seem to be elegantly and robustly engineered. 

I have hang-on filters (Aqua-Clears) on the bigger tanks in my (so-called) fish room. They come in a variety of sizes, the ones I have only cost $15 to $20 each by mail-order. They make a fairly loud "babbling brook" sound that I like, my wife doesn't, and is constant. Minor water splatter due to the waterfall effect. I break those down monthly too, it takes a few minutes to clean  'em out. 

(Note: I really lack the science to fully appreciate the arguments for and against activated carbon (the issue being whether under some circumstances, absorbed impurities can be abruptly released back into the tank), so I err on what I think is the side of caution and do not routinely use activated carbon.)

I also use sponge filters in some of my 10 gal tanks and in many smaller tanks and containers. They're cheap and work very well.  Minor water spray, depending on air flow. Works in a 10 gal tank whether there's 2 gals of water in there, 5, or 9 ... something that cannot be said for external box filters. But in my experience you quickly (15 or so tanks) get to the point where you need a serious air pump that costs perhaps $250 new or $100-150 used. On the other hand, other kinds of power filters would cost way more than that for the same number of tanks. At this level of fish-keeping, monthly electrical consumption becomes a relevant factor too ... I've seen some calculations where some kind of pump (?a vane compressor) putting out a couple of cubic feet of low-pressure air per second drew 66 W, which meant it's electrical operating cost all by itself was in the range of $65 monthly. In contrast, a linear piston pump for the same approx output drew only a couple of watts, and was therefore way-way-way cheaper to run. 

Sponge filters also make very perceptible bubbly noises all the time. Some people make their own (taking due care to make sure the sponge sheets they use are not pre-treated with chemicals to resist mildews.) Takes two minutes to clean them on the sporadic occasions I think of it, most of which is disconnecting them from their airlines. (We need quick-release connectors !) 

I have sponge-filters on a couple of 10-gal brackish/salt water tanks with killies, but I'm not real confident that's working well for that usage. However, I'm probably not doing enough water changes there, not as much as I do with the fresh water tanks. My jury is out on whether sponge filters are viable for brackish water use. Three out of five of my brackish water killie species seem to clearly prefer the moving water created by a power filter, though. 

On the do-it-yourself side, I have seen two things that seem appealing. 

The first is for a micro-filter than is essentially plugs of sponge (or cotton gauze) stuck into the ends of a std PVC "T" connection, and air-powered like a normal sponge filter. This thing is small enough you could use it to filter a peanut butter jar. (Stand up if this indicts you and your opportunistic/desperate fish-keeping practices. Wow, that's quite a few of you. Thanks, you may sit down now. )  Also reportedly excellent for fry containers etc where you might only have an inch or two of water depth. Reputed cost is on the order or 50 to 75 cents. 

The other is a small wet-dry filter perfected by Henri deBruyn, consisting essentially of a section of roof gutter partially filled with lava rock; an air-powered lift-tube carries water up from the tank so that it can drip through the lava-rock and back into the tank. Henri reports that, using this style of filter in Europe, he's been successful in breeding a large number of killifish handed to him by other good breeders who weren't having success, and he unequivocally attributes the difference to his use of this type of filter. Estimated cost of parts, less than $5 each. (And that could be a high-ball estimate. In preparation for my foray in production of this style of filter, I bought a 50-lb bag of lava rock last week in the garden section of my local home improvement store for a stunning $4. That's a reasonable price for filter medial, don't you think ... 8 cents a pound ?)  I have to search around for the link to the instructions, though. 

In the past, I have also used undergravel filers and powerheads for 20-30 gal salt and freshwater tanks. They seem to be out of favor presently, but I never found them to be more work, or less effective, than other types of common filters. I suspect this disfavor is largely due to the increased popularity of s/w "reef tanks" as opposed to "fish tanks" ... reef tanks have a LOT more carefully arranged stuff in them, and thus the annual-ish "complete breakdown" of an undergravel filer would be a huge pain. For a less elaborately set-up fish tank, they're probably still okay. Powerheads are good for fish that like a strong current, but they can be overwhelming for small fish and/or make the high-flow area of a tank uninhabitable. (Which could be okay, if you have other fish in the tank more than willing to occupy that micro-niche.)

I also currently have about 15 small tanks (2 gal Lustars and plastic "shoe boxes") that have no active filtration at all. But I'm doing 50-80% water changes twice weekly on those tanks, and I assume that my margin for error is small. 

* * * * * 
Regular water changes are important, even on filtered tanks. On 10-gal tanks or small tanks, I do a 50% change weekly.  On 20-gal or larger tanks, I'll siphon out 5 to 10 gals weekly, sometime more depending on tank conditions and the fish load. 
* * * * * 

Joshua Wiegert wrote: 

>>  Sponge filters, believe it or don't, are one of the 
>>  best biological and mechanical filters out there, 
>>  especially for their size and costs.  For most fish 
>>  keeping purposes, they make a great secondary 
>>  filter.  They're perfectly suited to quaranteen, 
> > breeding, and treatment tanks.  

Although as I say I have many sponge filters in use, I do NOT use them for treatment tanks or for quarantine purposes when the fish have a specific suspected problem. (As opposed to a precautionary quarantine of new arrivals or newly caught fish.) It takes a certain amount of time for the biological filter function of a sponge filter to become active, I don't know how to keep that going (without potential cross-contamination) for sponge filters that are "in and out of service" on a temporary basis, and I'm suspicious about the invisible impact on water quality of a reserve sponge filter that's been sitting around for a while with a negligible nitrogen load to keep the bacteria going. I also assume that between uses in a treatment tank, you'd have to boil the sponge filter to sterilize it, which would be a bit of a pain, and would obviously set the bacteria colony back to square zero. (When moving sponges from disease-free tank to disease-free tank, I usually just briefly shower and squeeze them out in faucet-hot water, hoping that's a decent compromise that gets rid of some of the possible bad stuff without killing off all the good stuff.) Therefore on treatment tanks, which tend to be small, a gallon or two, my general practice is to use no filtration and 90% or greater water changes daily. 

Other odd-ball thoughts in closing:
 - AquaClear-type hang-on filters are handy workhorses, it's always nice to have an extra or two around for contingency purposes
 - they also make great xmas or birthday list items to suggest to those relatives who really doesn't have any clue what to give you
- OTOH, a sponge filter or two can be easily dropped in that Igloo cooler of new-caught fish, and provide filtration and aeration for a few days ... most hang-on filters will only work if the water level is within a few inches of the lip of the container, and often won't hang on the round edge of a bucket. 
- did I mention water changes and siphoning out tank gunk??? Flush that stuff out of there !!!!



Doug Dame
Interlachen FL
"A cichlid tank needs a cichlid like
   a bald eagle needs a bikini."
- Wright Huntley (as quoted in 
Famous Things They Never Said, 
in press).