Personally, I don't think any would be worth the money unless you are keeping very delicate fish and even in that case, I would prefer to just do my own tests daily. The actual reading for pH is really of little concern. As long as it's stable, you are fine as most fish will adapt to what ever you have. I don't have a clue what it's talking about in "CF - conductivity factor" & "EC - electrical conductivity". I certainly don't know what they are on my tanks and don't know why it would matter. Maybe that's a factor with SW tanks but I don't think so. Probably to do with swimming pools or something. As for PPM, I don't know what it's measurng PPM of: ammonia, nitrite, nitrate, etc. That's pretty much a useless number. And you can get a $5 digital thermometer to keep a check on the temp.