Tetra - Whisper Power Filters
I have 3 of the Whisper 5/10's on 40 L tanks each. First one is on a planted tetra tank and I have DIY CO2 on the tank and 4 WPG lighting. I let the CO2 run right into the intake tube on the little whisper and it does great. Breaks up the CO2 into tiny bubbles and never stops. Plants grow like crazy! Second 5/10 is on my bio farm tank. Everybody should have a bio farm tank. I keep bio media from all my different filters I use in that tank and keep it fishless cycling all the time. It also has a Whisper internal filter, a spare sponge filter and box filter in it, with a 50 W heater on as high as it will go. Splash a little ammonia in the tank once a week and know the little whisper keeps it all moving. Third tank is a quarantine tank and it runs without fail in there also.
I have a whisper 40 on a 110 L planted tank with about 70-75 cm of fish. This filter is quiet, but it clogs too easily and then the water just runs over the inlet tube and back into the tank. The filter MUST be cleaned every week with the load I have or it will not clean the water. As far as the unit itself, I have no problems with it. It seems to pump a lot of water when the filter is clean. I would recommend it only for a lightly populated tank. For me, I'm switching to a canister filter.
I have read some of your comments regarding Tetra Whispers, mine is a 20, and let me tell you that after a year it's making a racket, with the sound levels increasing coming from the bottom of the filter, the intake tube area. Will probably buy a different brand when it finally becomes too loud.
My father bought this filter for my 75 L tank when he first got me hooked on fish about 20 years ago. It ran great for more than 6 years with no problems. I have recently 'dusted off' my old tank and got it up and running again. The only issue I've ever had with this filter is the impeller had dry rotted while in storage and I had to get a new one. I definitely give it a 5 star rating all around. If you have a Whisper and it starts making noise it's time to get a new impeller.
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