Welcome to the show-down! As keepers come to know, turtle tanks benefit from powerful filtration applied 24/7, mainly for biological filtration (converting ammonia to nitrite to nitrate, which is then kept dilute via water changes) & secondarily for mechanical filtration (removing particulates so the water looks clear & clean). Some even use activated carbon for mechanical filtration (makes the water look more crystal clear & may reduce odors, but fairly expensive & should be replaced monthly).

Warning: No external canister filter is going to vacuum crud off the tank bottom – they do not generate currents sufficient to do that. There will also continue to be free-floating minute particulates in the tank. Even a very powerful filter intake’s current rapidly diffuses outward, & exerts very little pull even a few inches away. The main purpose of a filter is biological filtration (converting ammonia to nitrites to nitrates; nitrates & other dissolved solids (i.e.: hardness) are kept diluted via water changes & you must do frequent large water changes no matter what filter you use.

The filters that give you the most power & highest media-holding capacity (i.e.: biomedia, mechanical filtration media, activated carbon) in the most compact form-factor (compared to, say, an overflow wet/dry filter with a sump) are the external canister filters. We typically recommend getting one rated for 2 - 3x’s the size of your tank. They are designed for fish tanks (water filled to the rim) & are more difficult to prime on partially filled turtle tanks than full fish tanks, & need to be kept at a lower level than the aquarium (usually in the tank stand under the tank). There are 3 major brand name lines to choose from:

1.)    Fluval 104, 204, 304 & 404 (not the 1, 2, 3 & 4 Plus line, which are internal canisters with less media capacity). The 404 tends to run around $115.

2.)    FilStar XP 1, XP 2 & XP3. The XP3 tends to run around $115, but biomedia may need to be purchased additionally.

3.)    Eheim Pro II 2028 (there are others, but this roughly $215 online ‘top of the line’ model is slightly more expensive but rated for a much larger tank than the 2026. There is a 2128 version with an integrated heater, although I prefer my heater separately. Eheim is a German company & Eheim is to external canister filters what German-made cars are to auto.s; a top-of-the-line reputation for quality at a big price.

In our community, the 2 best ‘bang for the buck’ powerful canister filters are the FilStar XP3 & the Fluval 404. Both have devotees & detractors, but if you’re an aquatic turtle keeper, you’ll probably be getting one or the other sooner or later (when you get a tank larger than a 20 gallon long). These 2 canister filters are discussed in ATP’s Product Reviews covering filters, and also in ATP’s Filtration article. You can start by reading those & learning which filter you need for your setup. But once you narrow it down to an XP3 or a 404, here’s where you need to be, because we get a lot of postings asking which is ‘better.’ So some of us decided this pinned topic would be useful. Special thanks to BobMc, who owns both & offers a balanced view.

1.)    FilStar XP3.

Manufacturer – Rena & also Aquarium Pharmaceuticals site info. is unimpressive.

Dimensions - 9 1/2" Long x 8 1/4" Wide x 15" High.

Hoses & Connections – The hose connections to the canister body swivel freely but the hoses are a rather inflexible semi-soft tubing – these 2 ‘features’ basically cancel each other out relative to the 404’s hosing & connector system. The Xp3 uses the opaque heavy vinyl hoses. They allow light to pass through and the end result is this gray green slime throughout the hoses that are under the tank lights (Note: this is believed to be harmless). The portion of the hoses under the cabinet and in the dark have no growth in them. Wherever the hoses are attached to rigid tubing, the over joined area becomes filled with a black substance that you can't get to. Once you make the Xp3 hose/tube connections it’s very hard to dismantle them. Fluval gives you enough hosing to reach the bottom of a 24" tall tank with both the intake and outflow assemblies. Having lots of hose allows one to twist the outflow into a position to that will agitate the surface. But the Xp3 spray bar is still the better surface agitator while the Fluval is better suited to creating a circular underwater current.

Media Setup – Intake water enters top of canister, runs down side to ascend through 4 media baskets & on top of those a fine mechanical filtration pad. The XP3’s media baskets are a bit larger than the 404’s, but the 404 also has a pair of sponges to pre-filter the water, likely more than making up for the difference. The XP3 has four sponges of varying density (each about 1/2" thick) ranging from a large open pore to a super fine pore, stacked large (on the bottom) to small in the lowest basket.

Rated (by Manufacturer) for Fish Tank Size – Up to 175 gallons.

Pump Rating – 350 gallons per hour.

Circulation – I saw no listing for this.

Energy Use – UL Listed 30 watts (per ThatPetPlace.com).

            Priming Difficulty – The XP3 has a rep. for fairly easy priming.

            Noise Level – marketed as quiet but some members report varied noise levels, most often a humming sound, that’s usually muffled by being in a cabinet under the tank. Bob says his is louder than his Fluval 304, stating “The noise is a low tone consistent hum, not such that you would even notice it in a busy room with day to day things going on.”

            Included Media – often sold without biomedia, in which case you must buy it separately (this is important).

            Outflow – Versatile! You have the option for a spray bar; unfortunately, if it’s vertically-oriented the top part may spray above the water in a partially-filled turtle tank. If it’s horizontally-oriented it may be above water in a partially-filled tank, making splashing racket. Consider sawing the spray bar off just above the holes, & using a piece of flexible tubing spliced in so you can reposition the spray bar horizontally just below the water’s surface.

            Special Notes – 1.) You may want to ditch the fine particulate filtration pad at the top of the media stack, if it clogs fast in your tank (more an issue in high particulate load tanks). This will cut down on servicing but also reduce fine mechanical filtration (Bob’s Note: Rena suggests replacing the pad every two months). The filtration baskets have handles. 2.) If you own a Glasscages tank - They are built with a 2.5" glass rim around the top. He builds the rim in to prevent escapes. Well....The rigid tubing of the Xp3 is only 2.25" wide, you have to either cut and re-attach the rigid tubing with soft hoseing like I did, or you can force it over the edge like some others have done. This rigid tubing is similar to model airplane plastic. If you stress it, you get that white coloring just beore it snaps. And you can't glue stressed plastic back together. The ‘feet’ are ~ 1/4" wide rubber buttons securely set in the base; Bob’s never had any fall off.

            Warranty - 2 year warranty.

            Cost: $95 – 115+ online.

2.)    Fluval 404.

Manufacturer: Hagen - reputable maker who also produces the Fluval internal canister & AquaClear filter lines. Hagen’s web site is much more impressive for info. resources on the 404 than Rena’s/Aqua.Pharm.’s are on the XP3.

Dimensions: Canister dimensions 6.5" (16.5 cm) depth, 9.5" (24.2 cm) width, 15.5" (40.0 cm) height, add 2-1/2" with hose.

Hoses & Connections - The 404’s hose-to-canister body connection is vertical & immobile, but the corrugated style of the Fluval hoses are much more flexible than the rather inflexible semi-soft tubing. So both filters offer adequate flexibility via 2 different approaches. Fluval hosing is a corrugated blue plastic that cuts and bends easily without crushing. They supply specialty corner brackets to hold the hoses in the U-TURN shape needed to go up and over the tank rim. The Fluval inlet tube that attaches to the end of the hose is a smoked plastic. There is no crud build-up in the corrugated hoses. There is a touch of gunk in the smoked tube. Fluval gives you enough hosing to reach the bottom of a 24" tall tank with both the intake and outflow assemblies. Having lots of hose allows one to twist the outflow into a position to that will agitate the surface. But the Xp3 spray bar is still the better surface agitator while the Fluval is better suited to creating a circular underwater current. With a 24" tall tank, The Xp3 with their rigid set-up is 6" short of the bottom on the intake, and the spray bar only reaches about 4" from the top of the tank. Which is fine if the tank is filled to the top. But you still have to stretch the inflow somehow to reach the bottom.

Media Setup – Intake water passes through 2 vertical sponge pads (which thus act like an additional media basket) before ascending through 3 media baskets (often 1 with mechanical media, 1 with chemical media (activated carbon) & 2 with biological media (BioMax)) before exiting the canister to the tank. The 404’s media baskets are a bit smaller than the XP’s, but the pair of vertical sponges to pre-filter water likely more than make up the difference (Bob estimates the media volume counting the sponges is easily 1/3’rd more in the 404 than the XP3).

Manual (PDF)

Rated (by manufacturer) for Fish Tank Size – Up to 100 gallons.

Pump Rating – 340 gallons per hour.

Circulation – 225 gallons/hour.

Energy Use – 22 watt power supply with 6 foot cord (per That PetPlace.com).

Maximum Water Column Height – 6.7 feet.

Priming Difficulty – the 404 has a varied rep.; some peoples’ prime easily & they’re never had a problem; some people are driven near mad trying to prime them & could hurl them from windows. There are work-arounds that vary in effectiveness for different people. Whether to fill the canister with water before priming has been hotly debated; some people find it makes a difference (likely due to partially filled tanks having much more air volume in the hoses).

            Noise Level – marketed as quiet. Bob says his 304’s are quieter than his XP3’; very quiet, in fact.

            Included Media – comes with everything you need, including biomedia.

            Outflow – There’s only one form, set up to discharge outflow across just under the surface of a full tank, agitating & oxygenating the water (It has a straight downtube ending in a ‘U’ shaped tube with a horizontal outlet. It only requires a slight upward angulation to point at the surface. You can set it right at or below the surface). In a partially-filled turtle tank, this discharge is intolerable & if evaporative losses drop the water level it’ll make more noise. You can remove the outflow U-shaped tube & jam a piece of aquarium tubing over the down-pointing outflow pipe, so it discharges under water. Much less versatile than the XP3.

            Special Notes – 1.) There’ve been a couple of reports of the company giving good service & standing behind their products. I found their web site more informative on the 404 than the manufacturers’ sites on the XP3. 2.) Bob reported some have complained of handle clamp breakage. His Fluval 304’s are over two years old. He’d never had clamp breakage or anything close to it. He wondered how others broke theirs. Then last time he did filter maintenance, he couldn't get the Fluval lid on. He saw if he forced it much more, he’d break one of the lid clamps. He checked the gasket & the baskets to see if they were sitting right. After about four tries, he noticed the lid had gotten spun around and that he was forcing the power cord down into the wrong side. He suspects others broke their lid clamps doing the same thing. For ‘feet’ the 404 uses 4 little rubber bars turned sideways and pressed into plastic grooves.

Warranty – 3 year limited warranty.

            Cost: $85 – 115+ online.

Notes: The priming issue is the make or break for the Fluval 404; you either have the problem or you don’t. If the absolute quietest filter possible is needed, the 404 may have the edge. While the XP3 is rated for a much larger tank, those ratings come from the manufacturers & we don’t know how they were arrived at or whether a direct comparison is legitimate. That said it is rated for 175 gallons to the 404’s 100 gallons. The XP3 has a more versatile output system. 

BobMC’s Head-to-Head Comparison of the FilStar XP3 vs. the Fluval 404.

Note: Bob has 304’s, the next step down from the very similar 404, & an XP3.

 It's really a toss-up here. I have both.
They both do a very good job.

Priming: I don't consider the Fluval 404 difficult to prime, but the FilStar XP3 does have a quicker system........XP3 wins.

Hose Connection to Canister: The hose lock detachment set-up on the XP3 is a single valve set-up, unlike the Fluval with a shut-off valve and then a (very flimsy) unlock lever. It always feels as though it's about to break off, when I'm trying to detach it............XP3 wins.

Output Options: The XP3 comes with three different outlet set-ups. The Fluval only has the one. The catch here is that the Fluval’s flexible hoses allow for better placement, while the rigid tubing of the XP3 limit where you can put your in- & out-take tubes..........TIE

Tubing/Hose: I had to saw through mine (XP3 tubing) and re-attach with clamps and soft tubing to get my tubes where I wanted them (Drrich’s Note: The Eheim Pro II uses tubing between outflow pipe & spray bar, so such flexibility is built-in into the design).

Another issue with the tubing is that the XP3 tubing, being both rigid and multi-jointed, in theory has many places for air to leak into the system. The Fluval tubing, having no joints, in theory eliminates this problem..................Fluval wins.

Suction Cups: Suction cups across the board are crappy. Both brands harden up and start to fail within a year. I've had to replace all of mine. Maybe it’s my water, I don't know.

Media Baskets: The Fluval 404 has 4 media baskets and a sponge section while the XP3's sponge section is the bottom basket, thereby leaving you with only two media baskets..........Fluval wins

Subjective Build Quality: The XP3 overall is made out of a heavier, thicker plastic than the Fluval, in both the canister and lock handles, and has a sturdier feel to it............XP3 wins

Price online: Very close, either about the same or with the FilStar XP3 perhaps $10 more, but you often have to pay a little more to purchase XP3 biomedia separately.
.........................................................Fluval wins

They both have good points and bad points, now if some manufacturer could just combine the best of both, he could make a ton o'money.

Good Luck,
BobMc & Richard.

Appendix I: The Eheim Pro II 2028.

            I had a special request to cover the Eheim Pro II 2028, but most people aren’t willing to pay the $100 premium & I didn’t want to confuse the already dense comparison between the FilStar XP3 & the Fluval 404. We’re compromising with a brief discussion of the 2028 here in a separate appendix.

3.) Eheim Pro II 2028.

Manufacturer - Eheim – a German company with likely the strongest brand-name in the U.S. today for making canister filter.

Dimensions – 17.9" Tall x 8.3” x 8.3.” 1.9 Gallon volume.

Hoses & Connections –Where the hoses connect to the canister, they are flexible & come off at an angle (not straight up like a 404, & don’t pivot about like an XP3). You hold down a red button & pull up a level to release the hoses – learning to reattach them smoothly after serving can be a bit tricky. Don't get ahead of yourself hooking up the hoses - you'll need to cut a strip off one to hook the outlet to the spray bar (once I pushed a hose over the intake piece, I couldn’t pry it off; I had to cut it off. I was able to pull the hose off the outlet attachment, though). Just don't hook up the intake and output prematurely; do it in the order the manual says. The Eheim uses semi-transparent green 16/22 mm tubing; you may have trouble finding this (the 404 uses 1/2 inch; it's all over the place). (Note: You get all the hose you need for a basic installation in the box, so you can run it right out of the box). I wanted some extra hose & couldn't find a supplier. I e-mailed Eheim & was referred to BigAlsOnline (they carry it).

Media Setup – The 2028 lacks the sponges for initial filtering that the 404 uses. It only has 3 media baskets but they’re much larger than the 404’s. Instead water enters the top of the filter, goes to the bottom, rises through the 1’rst large media basket (containing Ehfimech, hollow ceramic cylinders for coarse mechanical filtration), then through a blue sponge pad (seldom clogs, easily rinsed out, reusable), then up through the other 2 large media baskets (with biomedia), then through a white fine filtration pad. That fine filter pad can clog fairly quickly (in a few weeks) on a high particulate load tank, despite thorough rinsing will clog quickly if reused, & I chose to toss mine (forsaking some fine filtration in order to only service the filter ever few months when flow drops off). There are different biomedia you can use, even Eheim-brand options – mine came with Ehfisubtrat, a specially designed sintered glass product looking like medium white aquarium gravel & feeling a bit rough/sandy to the touch. Ehfisubstrat Pro is formed into balls, & I saw a 2028 with media at Big Al’s that pictured the Pro media. There are media options like fiber pads with activated carbon, & you can put whatever you want in the media baskets.

Manual: The Eheim manual is multilingual, and English isn't the first chapter presented. The manual's pretty decent, although sparse (so's the Fluval, by the way).

Rated (by manufacturer) for Fish Tank Size – Up to 158 gallons.

Pump Rating – 277 gallons per hour.

Filter Circulation – 198 gallons/hour.

Energy Use – 25 watts.

Maximum Water Column Height – Per the manual for maximal functional safety there should be no more than 180 cm (~ 71”, or just under 6 feet). That’d be based on a fish tank completely full; it’s hard to say how it applies to partially-filled tanks.

Priming Difficulty – A big round ‘push II prime’ pump head is pushed in & let out to prime the 2028. Like other external canisters it’s made for fish tanks filled to the rim, so it’s tougher to prime on turtle tanks but can be done. You prime the canister before you plug it in, and if your tank is tall with a water level a few inches below the top, it doesn't work on an empty canister. That’s confusing because the manual instructions state you push the disc to prime the dry, empty filter. Save yourself the grief I went through; fill the canister up, put the head back on, hook it up and then prime it.

Noise Level – Of my 2, one’s real quiet & the others fairly quite (some hum), but overall I’d describe the 2028 as a quiet filter fine for the family room. Most canisters are kept in stands under the tank which muffle the sound well.

Included Media – Here’s where you’ve got to be careful. The 2028 is often sold without media! You must get a deal with media including, because buying separately is expensive. I often find bundled deals with 2028 & media at Big Al’s Online. The 3 media baskets each hold about a liter of media, so you’ll need a liter of Ehfimech & 2 liters of Ehfisubstrat (regular or Pro). The blue sponge pads are easily rinsed & reused but the fine filtration white pads are not; beware the 3 pad packs with 2 white pads & one blue. If you choose to use the white pads, buy the 3 pad packs of all fine filter pads.

Outflow – The intake’s unremarkable but the outflow shows quality Eheim engineering. The flexible hose from the canister attaches to a rigid plastic elbow that hooks over the tank rim, then turns out a bit. Instead of sticking the spray bar on that piece (which would be nearer the XP3 approach), you cut a piece of flexible hose (pick your length to suit what you want to do with it), stick one end on the rigid piece, & jam the spray bar into the other end. This puts the spray bar on a flexible hose, whatever length you want, great for positioning it at whatever depth you like.

Special Notes – The Pro II 2028 has a more ‘high tech’ stylish look than the 404 or XP3. It has a Water Flow Ball Display on the pump head – a little white ball that roughly gauges flow rate (I don’t use it much; I watch the spray bar in the tank to judge flow). The canister's bottom has 4 little rubber feet; they pop off easily, are small, and easy to loose. Watch it; I'm lucky I noticed 3 of mine fell off while I was fooling with it. The suction cups get hard & hard-to-work-with, like the 404 & XP3’s. The Pro II 2126 & 2128 have a 210 watt integrated heater (although a sensor still goes in your tank) but I prefer to use separate submersible heaters. Per the manual the 2026 & 2028 are fresh or salt-water capable but the 2126 & 2128 are fresh water only (sea water-resistant version available, though).

Warranty – 3 year guarantee.

Cost: $200 - $235 ($215 with media is a fine price).