Marina Floating Thermometer for Betta Fish Tank with Suction Cup, Aquarium Thermometer, 11201A1

I was using one of those ubiquitous cheap digital thermometers on Amazon. The temperature fluctuated a lot with it. And I just really started to doubt it. I ordered this guy and it was 6 degrees hotter than the digital! Sure enough the digital thermometer was way off by 6 degrees! My poor fish was in 86 degrees water for a month. I am new to the hobby. And he is a betta....so this is the extreme end of the high temperature range. I'm just so glad I bought this.I tested this in a cup crammed full of ice and some water. This temperature read a perfect 32 degrees....this is how you calibrate a thermometer. The digital thermometer read 26. I don't think i'll ever be able to trust a digital thermometer again.The suction cup is glued in place. You can not swivle the thermometer to face a certain way. This doesn't bother me as it ws so cheap.This is $2.49. It works great. And is easily hidden behind a plant. I think the people who said the suction cup broke....or left a mark....i'm pretty sure those reviewers have acrylic tanks. Probably low quality acrylic.This is a $2.49 thermometer that is 100% accurate.UPDATE: i have now tested this thermometer against a few digitals. One being a very expensive digital. This thermometer is spot on accurate.

A thermometer is probably the cheapest thing you'll buy for your aquarium, but essential to keeping an eye on temperature fluctuations to keep your fish happy, and the easiest way to check how well your heater is working. This one works great, is inexpensive, and appears accurate. It stays securely attached to the wall of my aquarium with the suction cup, but even when I've knocked it off while cleaning, it's nice that it floats and is easy to grab and re-attach. It also feels well-protected and like it would be difficult to break. I would recommend this style of thermometer (a real thermometer, inside the aquarium) over the sticker-type thermometers that go on the outside of your aquarium, which can be harder to read and are more likely to be inaccurate.

This is a very basic, simple thermometer that sticks to the side of the aquarium well and does not take up much space inside.Since it is a mercury thermometer, it is very accurate. It has a clearly marked "safe zone" that can be seen easily. The only downside is because it is so small it is almost impossible to see the numbers if you need a precise measurement.For a basic community tank where you are looking for that 72-78ish range this works well. It confirms that the heater is working correctly and the fish are not too hot or too cold.

I bought 4 of these because I loved how they looked. It is very accurate, the suction cup works flawlessly, unlike other suction cups who don't do their jobs. If you so choose, the one I use in my pre treated water bucket for water changes, I just keep it in there without the suction cup and it does like it says, it floats! So I can grab it easily and make sure the temp is the same as in my aquariums and when adding more water to the bucket and rinse it out I just stick it to the side of the bucket while I rinse and repeat and it sucks on really well and never falls off the tub when I'm emptying it, so it works! It sticks and stays that way unless I use my nail to dislodge it from the wall of the bucket.

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It's not expensive and it works very well! I like the green color where it marks 70F/20C the perfect temperature for my Siamese Fighting fish to be living in. It sticks to the side of my tank very well, I keep the suction cup out of the water on my tank/bowl.Update (5/2014): So I've gone through three of these, and the main thing is they are EXTREMELY fragile, I tapped it against the side of my tank and it broke, also the suction cup gets weak if you take it off to clean the tank often. So it does what it's supposed to for a relatively cheap thermometer but I don't want to deal with the hassle of it breaking again.

The attached photo has one of these thermometers on the back left and right side. They were sticking well for a couple of days. Then they started floating and not wanting to stick. I just wiped the suctions off with a dry cloth and and they stick again. The temperature is easy to read for good eyes. I can see it clearly but my husband cannot. I have a electric heater that has a digital temp on it. It and both thermometers read the same.

I'm not sure what product other reviewers received, but the Marina thermometer that was shipped to me is VERY easy to read. Even has a green area to indicate the perfect temp range for most tropical plants and fish.YOU MUST READ IT STRAIGHT ON **see photos** Cannot be READ FROM SIDE VIEW. Simple fix, you adjust the thermometer within the suction cup and VIOLA! Just BE CAREFUL WHEN ADJUSTING, IT IS GLASS AND WILL BREAK. duhVery inexpensive & accurate.No batteries to replace? I'm in.Unobtrusive (@ 5" long) and easily hidden if desired. Personally I do not mind the way it looks in my aquarium.Hope this helps!