I've experimented with my own dosages of the Fluval Shrimp Mineral Supplement. I have 18.9L containers for my R/O water so I dose approximately ~7.5mL because pouring 10mL of the Fluval Shrimp Mineral Supplement will give me 6gH exactly. So dosing ~7.5mL will give me a range of 4-6gH which I desire (I aim for 5gH).
In this thread you see people doing their own dosage tests (since the dosing instructions on the bottle will not tell you the volume of water lol, you'll see when you get the bottle or when you read this thread):
http://www.plantedtank.net/forums/showthread.php?t=135520
I measure 5mL using the test tubes given by the API test kit. So I just pour the Fluval till it hits the white line on the tube then pour it into my 18.9L R/O bucket.
If you don't have 18.9L containers lol or don't plan on getting those big empty jugs, dose small amounts of the stuff (like 2.5mL at a time) to find out what dosage works for you in whatever container you store your R/O water in. Adjust accordingly each time you find out what gH you are at when you measure it until you hit what gH you want.
You can either find out how much you need to dose each time for a water change (AKA when you need to do a water change you pour your R/O water out into a separate container and dose the water in the separate container then pour it into your tank) OR
I personally just dose all of my R/O water (all 18.9L of it) so I don't have to worry about it every-time I change my water, and just pour it into my tank.
Just note when you dose the R/O water with fluval give it a good shake and let it rest for like 3-4 hours so the minerals get dispersed throughout the water evenly so when you test it you don't get inaccurate results (but then again it's because I have 18.9L of water so you could probably get away with less resting time lol).
Good luck finding out what dosage works for you (hopefully what I wrote is clear since I'm half asleep, time for bed).
