APERA INSTRUMENTS AI485 DO8500 Portable Optical Dissolved Oxygen Meter Kit, Auto Compensation for Temperature, Air Pressure and Salinity, GLP Data Management

This was my first DO meter. I am a commercial fisherman and we like to pack the house as much as possible. This has really upped our game when it comes to loading the tanks and knowing if there's room for more or if we need to take some out. Reads fast, easy to adjust settings, we have our salinity set at 4 ppt and the readings seem very repeatable. I've seen the DO meters with the membrane and they seem fragile and alot like a hassle. This one fires right up, has a good backlight, reads good even in dirty water, and hasn't failed us in 4 months of hard use. I probably got 20-25 hours out of a set of batteries. Keep some spares handy. I would like to have a longer cord for testing oxygen and temp deeper in the water column.

thanks for free gift. let's see if it is really free...

I had been wanting a Koi pond for years. My husband said they were too much work and one day I decided to have one put in thinking, how hard could it really be? They are just like big goldfish right? Yeah, no that's not really how it works and I kept killing off fish. Then I realized water had to be tested for different things (including oxygen and ph levels) and that testing the water wasn't nearly as easy as it should be in some cases. For ph you just dip a strip. For oxygen it was a whole darn process. This device makes it SO much easier. The readings are pretty accurate. Always very close to each other when taken minutes apart. For my needs it's fine but for someone who needs exact spot on measurements every time this could pose a problem. That's why I had to deduct one star. For simplicity of use and quality (it comes in a nice hard shell tool type case) it would definitely get five stars.