








💧 Keep it clean, keep it quiet — your aquarium’s new best friend.
The Tetra Whisper 40i Internal Filter is a compact, submersible filtration system designed for 20-40 gallon aquariums. Combining a quiet air pump with a 3-stage filtration process, it filters up to 170 gallons per hour while oxygenating water. Its internal mounting clip allows tanks to sit flush against walls, and the easy-to-replace Bio-Bag cartridges trap debris and fish waste efficiently. Trusted by hobbyists for decades, it delivers reliable, low-maintenance performance that keeps aquatic environments pristine and peaceful.

| Customer Reviews | 4.2 out of 5 stars 22,152 Reviews |
T**R
Love, Love This Filter!
Okay so... I have a 20 gallon temporarily for my 4 inch turtle. I accidentally bought the smallest of this tetra filter, so I bought the medium sized one in it's place. I had only had the tank filled halfway anyway since my turtle was only 1.5 inches at this point. Mind you I didn't realize how fast they grow, and had no idea that Its recommended to have a filter that can filter 2 to 3x the tank size. So I decided to keep both filters in my tank. One on each side. Even though I still don't reach the recommended filter size, my water now almost filled to the top, stays absolutely clean. Turtles are pretty messy so I still have to do the weekly cleanings and all that extra stuff that apparently those who spend hundreds of dollars on filters still have to do as well. I don't know if this is some kind of luck thing, I don't know if maybe my turtle just isn't that dirty (yea right, I see him)... but I'm actually not looking forward to switching out my filter for the 'recommended' filter size, as these filters work so good. I love them. They are both very quiet. Aside from the sound of the water falling back in.. I mean it sounds like a waterfall. Who doesn't want to hear a waterfall? I love it. This can also be prevented by raising the water level or lowering the filter itself. Basically the closer it is to the water, the quieter it is. Such a simple device, yet so beautifully sufficient. The little one stopped working at one point and I thought... welp there you go! Get what you pay for. But nope! Removed the base, pulled out the magnetic spring propeller and tube, cleaned it out and like magic it started right up as soon as I plugged it back in. Love how easy it is to replace the filters. The filters themselves are great and definitely hold on to some dirtiness. One thing I'll say is there is quite a bit of unused empty space. I now take advantage by adding some extra media, but I must say that these filters work great even without the extra. Love this filter and would recommend above any other filter.
D**T
I love these. Still going strong after 5 years. Bigger one and smaller one
I have used these for so many years for little tank setups and my turtle and snails etc. Always work super great and super quiet! Plus they are cheap. No brainer imo. I'm sure theres a faulty one here n there as with anything but keep the propeller clean like any other pump and dont let the filters get too overflowing clogged and you'll be happy I promise. Also with filters of any kind try to get one rated for more than you actually have so the filter doesn't get overwhelmed. Even the filters are cheap for a box of 12 for like $13. Cant go wrong!! 10/10
C**A
Works perfectly – great quality
This product works perfectly and does exactly what it’s supposed to do. My aquarium looks cleaner and healthier, and everything runs smoothly. Great quality, easy to use, and worth every dollar.
E**G
Big improvement
Big Improvement over the previous model. My small tank came with the previous version of this filter and it has a quite significant design flaw that twice caused the unattended tank to lose almost half it's water. Essentially, if the filter was at all clogged with particulate, water pressure would cause the water level in the filter to rise to the point it would flow out of the tank on the clip holding the filter to the edge of the tank. After the second time this happened and a lot of luck that it didn't fry my power strip, I decided it was time to switch filters. While I was prepared to move totally away from Tetra due to my upset over the previous situation, I noticed while researching the change in holding clip. The new design obviously is in reaction to the problem I encountered as it now is architected that even if water were to move back onto the holding clip, it would drain down into the tank as the attackment to the wall is lower on the body. Since I pretty much liked everything else about the design, I decided to give the new version a try. Price-wise it was reasonable and the noise level is very low. Once I received it, it was easy to assemble. My one complaint would be that the box contained two suction cups, but there is no instruction on how they are to be used. That said, I was able to position the filter very easily and the updated design allows it to be placed in such a way that it doesnt interfere with the tank cover. That had been a big complaint I had about the previous design. It was very quick to assemble, get in place, and start using and the speed of the water flow seems appropriate for the smaller tank size. Cleaning is easy since it essentially is just replacing the filter periodically. They do recommend on a yearly basis cleaning the impeller, which should help it last longer.
A**R
STINKY, NOISY, and WILDLY Inconsistent
FILTER #1 - A slightly smaller version of this filter came with the 5-gal 'Tetra Aquarium Starter Kit' we purchased. That one reeked of burnt plastic or solvent from the moment we unpacked it. Stinky odor persisted even after staging it in a 5-gal bucket for several days before fish. As others have reported, we also found this filter can be quite the noise maker. FILTER #1 - SMELLY, NOISY JUNK. FILTER #2 - Concerned that stink and racket wouldn't be healthy for fish or us, bought another filter, reasoning that the cost of Starter Kit PLUS a new filter would be tolerable. Ordered what we thought was the same filter (but hopefully without stink and noise). What we received is the 5-10 Gallon Whisper Internal Power Filter, which turned out to be a slightly larger version of what we started with, but which still used the same size 'M' bio-bag. When we staged it in the bucket we were pleasantly surprised to find it was slightly more powerful than #1. But most importantly, IT DIDN'T REEK and IT WAS ALMOST COMPLETELY SILENT. This one turned out to be a keeper and is presently in the tank with fish. FILTER #2 - EXCELLENT. FILTER #3 - Believing we had found a good filter, and wanting a spare, we ordered another 5-10 Gallon Whisper. It arrived with a hint of the same odor as #1, but we were hopeful that would 'just go away' after a few days of running in the bucket. But when we ran it in the bucket, we also noticed it was a bit noisier than #2. Then it quickly became a LOT noisier. But then, worst of all, we found evidence of mineral deposits from what must have been a very lengthy previous ownership (based on the LARGE amount of deposits). That's right, this thing was USED! FILTER #3 - STINKY, NOISY, USED GARBAGE FILTER #4 - Allowing that an unscrupulous consumer might have returned a 'used' filter to Amazon as 'new', or something similar happened in the Tetra/Spectrum supply channel, we returned/exchanged for another 5-10 Gallon Whisper in hopes of receiving another unit like #2. Not a chance - #4 was as noisy as #s 1 & 3. Back to Amazon it goes. FILTER #4 - NOISY JUNK So, we're done with Tetra/Spectrum filters. Based on our 25% success rate, I can't understand how these things could possibly have gotten the high ratings they have. There's no telling what's behind the problems we ran into, but the end result is a string of bad experiences with Tetra/Spectrum. No point in risking any more of our time or the well being of fish with this nonsense. We'll be looking elsewhere or going the DIY route - PLENTY of ideas on the web for fabricating what appear to be excellent performing filters from inexpensive and commonly available supplies, media and pumps.
F**A
Very reliable, well made and priced very fair.
It works great and is priced very fairly. I have had fish tanks all my life and love the product in all my smaller fish tanks where I store baby fish and or fish that have been picked on. It will last a long time if you take proper care of it.
T**I
Can't use lid
Working well in my turtle tank. The clip fits on the side well but you can not have the lid on if using the side clip.
L**S
Great product
Cleans Great and fast.one of the best filters for your money.
Trustpilot
1 month ago
3 weeks ago