TDS and PH meter

[carpetlover]

Has anyone used these kinds of meters before? It’s pretty cheap, which is why I’m wondering if they are reliable enough to use on reefs?

 

[Saltyreef]

I use a $100 tds/ph/temp meter. It calibrates and is very accurate. Oakton brand. I would not trust these myself.....

 

[Mike konesky]

3 hanna 98129s here. I dont trust cheap meters either.