API Master Test Kits

[Cermet]

The substrate can store toxic chemicals like a sponge - a single 90% water change will do far more than three 50% water changes (first: 10 ppm * 0.5 = 5 ppm; next one: 5 ppm * 0.5 = 2.5 ppm; third one: 2.5 ppm * 0.5 = 1.25 ppm. Now a single 90% is: (10 ppm - 10* 0.9) = 1 ppm. So a 90% W/C gives 1 ppm but THREE 50% W/C give 1.25 ppm!!!!

Note the math. It is tricky for values that aren't 0.5. For example: a 75% W/C is NOT 10 ppm * 0.75 = 7.5 ppm!!! Not correct. It is really 10 ppm - (10 *0.75) = 2.5 ppm left. The 0.5 is a special case that works by simple multi. In a similar fashion, a 25% W/C is 10 ppm - (10 *0.25) = 7.5 ppm left in the tank. Try this method for 0.5 and it still works.

[Goes to 11!]

Massive +1 to the previous two posts.

[Rocksor]

what everyone else said

[Shidohari]

The substrate can store toxic chemicals like a sponge - a single 90% water change will do far more than three 50% water changes (first: 10 ppm * 0.5 = 5 ppm; next one: 5 ppm * 0.5 = 2.5 ppm; third one: 2.5 ppm * 0.5 = 1.25 ppm. Now a single 90% is: (10 ppm - 10* 0.9) = 1 ppm. So a 90% W/C gives 1 ppm but THREE 50% W/C give 1.25 ppm!!!!

Note the math. It is tricky for values that aren't 0.5. For example: a 75% W/C is NOT 10 ppm * 0.75 = 7.5 ppm!!! Not correct. It is really 10 ppm - (10 *0.75) = 2.5 ppm left. The 0.5 is a special case that works by simple multi. In a similar fashion, a 25% W/C is 10 ppm - (10 *0.25) = 7.5 ppm left in the tank. Try this method for 0.5 and it still works.

Oh believe me, if my readings are that bad i automatically vaccum my gravel. the other problem is a full 2.5 bucket in my case is all i can safely carry without chance of dropping it. So i had to do two to three water changes in the same day one after the other to ensure i covered everything.

[Dave Waits]

I vacuumed all my gravel during the first and second 50% changes.

Aha! There lies the problem Cermit! three 50% changes didn't change the reading at all. That was three 50% WCs within three days.

[Dave Waits]

As an experiment, take a store bought water bottle and test the water in it. If it gives a weird result there is a good chance your test kit may be messed up or expired.

Here is how to check the bottle to see if it is expired.

Each reagent bottle has a Lot # printed
on the bottle. The last four digits are the month and year of
manufacture. Example: Lot # 28A0102. This is a pH reagent manufactured
in January of 2002. Pond Care Wide Range pH, ammonia, High Range pH,
Nitrate, phosphate, Copper, calcium and GH all last for three years.
nitrite and KH will last for four years. Freshwater pH(low range) and
Pond Care Salt Level will last for five years. I would not trust these
kits after they have expired.

Info was found on
http://www.fishlore.com/fishforum/te...kit-users.html

Lot number on my Nitrite bottle says;Lot 26AO712 EXP.07/2017 so, it was made in July of this year.