API test tubes not relible

[Incredible Corals]

Tested Calc today and pulled 5ml of water out of the display and added it to the API test tube that comes with the kit. The API tube has a mark that says 5ml. I took 5ml of tank water with two different syringes and it's about 1.5 to 2ml over the 5ml mark on the test tube. So the mark on the API test kit is way off. My question is do I still fill it up to the line on the test tube or actually fit it up with a true 5ml of test water? Not sure if the test kits are calibrated to the amount of water that is on the line of the test tube which is probably 3.5ml or 5ml of water.

 

I think this is pretty serious because you could overdose or really under-dose your tank with alk or some other supplement.

[Marc Weaver]

I would use 5mL and stick with that as long as you are sure it is 5mL. I have a few API kits and the lines are all different!! Hanna checker vials are the same way.

[Incredible Corals]

I would use 5mL and stick with that as long as you are sure it is 5mL. I have a few API kits and the lines are all different!! Hanna checker vials are the same way.

 

That is crazy. I can't believe I just figured it out.

[Marc Weaver]

Check it both ways and see if there is any noticeable difference. I don't remember if there was when I did it.

[Origami]

Use 5 ml. I've had the same issue with some of their tubes. The solutions are mixed to operate on a 5 ml sample. If the tube is off, you'll likely get a bad measurement.