I hate test kits!

[Delphinus]

I think that's key. I think what's more important is the ballpark figures and the week to week trending.

[pterfloth]

If you really want accurate alkalinity results then you can do what we do in the water treatment industry, use methyl purple indicator and N/50 sulfuric acid to titrate. The N/50 sulfuric acid is very dilute and harmless. Using a 50 ml sample of tank water, add 4-6 drops of methyl purple indicator and add N/50 acid until the color changes from green to purple. Every ml of acid added is 20 ppm of alkalinity, so 6.5 ml = 130 ppm alkalinity (dKH 7.3). A 4 litre container of N/50 sulfuric acid is about $82.00 from Fisher Scientific. That's good for over 600 tests!

I also use an industrial test method for calcium and magnesium. It's 100% accurate and much cheaper in the long run.

The commercial test kits are not very good and very over-priced. Like the commercial liquid calcium and magnesium additives, the mark-up is scandalous.

[mark]

The one before my last Salifert test kit came with a Alk check solution. Maybe put up a post looking for some.

btw, both my kits check at 7.0dKH with it.

[Hairytank]

I have the API test kit for dKH and Ca and have found them consistently low lately...6-ish and 380-ish. However, when I dose up to a dKH of 9 and Ca of 420 according to the API test the colours are way better in the acropora so I suspect the tests may be correct....I am soooo confused-ish...

[fishytime]

Ok so I tested again this morning....

API 8.5
Salifert 12.5

tested the check solution which is labeled 7.3....

and got 11.5 *wonders if salifert tests the check solution with their test kits*

so if I subtract 4 from my 12.5 reading I get 8.5 which is what the API test reads


The second salifert test kit from the shop was off the charts...according to that one my dkh is over 16.


I hate test kits!

[whatcaneyedo]

Originally Posted by pterfloth

If you really want accurate alkalinity results then you can do what we do in the water treatment industry, use methyl purple indicator and N/50 sulfuric acid to titrate. The N/50 sulfuric acid is very dilute and harmless. Using a 50 ml sample of tank water, add 4-6 drops of methyl purple indicator and add N/50 acid until the color changes from green to purple. Every ml of acid added is 20 ppm of alkalinity, so 6.5 ml = 130 ppm alkalinity (dKH 7.3). A 4 litre container of N/50 sulfuric acid is about $82.00 from Fisher Scientific. That's good for over 600 tests!

I also use an industrial test method for calcium and magnesium. It's 100% accurate and much cheaper in the long run.

The commercial test kits are not very good and very over-priced. Like the commercial liquid calcium and magnesium additives, the mark-up is scandalous.

Does a person have to use a 50ml sample of tank water? Could I use half that and then 2-3 drops of methyl purple and then for every 1/2ml of sulfuric acid the solution is 20ppm of alkalinity? I ask because $97.95 for the 4L acid and $13.85 for 120ml of the dye plus some tax and shipping for +600 tests isnt much of a deal. But getting twice that many would then make the idea start to make sense.

The cost looks like it would be about $130 for 600 tests which means I would get 4.6 tests for every $1 spent. A seachem alkalinity kit is about $18 for 75 tests which is equal to 4.1 tests per $1. Then again most of us only test once a week at most so 600 or so tests would last 12 years... I think this might require a group order.

https://ecat.fishersci.ca/(fw4tt355o...aspx?cid=20639
https://ecat.fishersci.ca/(fw4tt355o...px?cid=3640757

[midgetwaiter]

FWIW the only fresh alk kits I've ever had trouble with are Salifert. I've seen Nutrafin kits get wonky after 6 months or so but fresh ones are usually pretty good and the replacement solution is only $3. Never used Elos much, seems to me like it's the same indicator as the Nutrafin at a different concentration.

You'll never know what is up for sure unless you have a standard to check against. If you have a scale that measures grams you can do this:

1L RO/DI + 148g dry sodium carbonate should give you a 140ppm | 2.8 meq/L | 7.8dkh solution.

Get sodium carbonate (washing soda) by picking up some Aquarius pH+ pool stuff at Crappy Tire.