Ruth,

The RO/DI water had been heated and aerated since last Sunday after the water change. The salt was added, fully dissolved, then aerated for about 20-30 minutes before testing.

BTW, we mix the salt into the heated and fully aerated RO/DI water not longer than 24 hours before using. After about 36 hours, we've noticed that something precipitates out of the salted water, which could explain your different readings. Or, if you start out with cool, unaerated RO water when you add the salt, you could also get different readings after it has been aerated and heated with the salt in it.

That doesn't make sense to me. If it is going to percipitate out in a mixing bucket aireated and heated it is certainly going to continue to percipitate out in your tank aireated and heated.

Maybe it's the mixing container (rubbermaid trashcan) that causes the problem, though when we used a glass aquarium years back, there was precipitation after a period of time, too. I think in a tank all kinds of chemical reactions happen with various components of the saltwater, and unless one chemical component is seriously out of whack, there won't be any precipitation.

Really, I don't know. I'm only guessing. But these have been my observations.

If we have leftover saltwater after a water change, we just dilute the leftover water more RO/DI water. Precipitation does not occur then.

Beverly,

Last night, I also tested the Kent from the recent group order and got a dKH of 9. I also used an Aquarium Pharm test kit, and it doesn't have the .5 resolution you mention. 1 drop of reagent = 1dKH. Are you interpolating between two drops, or did you use 2ml of water and halve your input drops?

Matthew

Still doesn't make sense. I know people (myself included at time that keep mixed up salt water, heated and aeriated) in case an emergency water change is needed. I also use a rubbermaid trash can and have never noticed anything percipitating out. I have noticed changed on freshly mixed water in the first 24 hours but not after that. I mean most of the trace elements, calcium and alk. that goes into our tanks comes from our salt water. The only other chemical to cause a reaction are those that we add and I don't think we would want to be adding anything that is going to make calcium, alk/DKH, or mag. percipitate out (those being the most common things we test for and really all I test newly mixed salt water for). What have you noticed that has percipitated out after 24 hours? Just curiious and trying to understand this.

I have Coralife salt bucket and the salt is in 3 sealed bags.

Tropic Marin is in one big bag inside the bucket as well. I haven't opened any of the Seachem buckets yet as I am using the boxes up first and they each contain 3 50g bags.

Matt,

I don't know what "interpolating" means :razz:

What I did was add one drop at a time, then mix as per directions. At drop #8, the colour changed from blue to green. From experience, I know that the next drop will turn it yellow. So I am guesstimating that the real dKH is 8.5 from the intermediate green colour.

Maybe that's "interpolating"?

Ruth,

I have no idea what is precipitating out of the saltwater mix after 36 hours. I don't test my NSW, and am not really that curious to know what precipitates out. I just know to use it within 24 hours after salting it. Sorry I can't be of more help here.

[quote=Beverly]

After about 36 hours, we've noticed that something precipitates out of the salted water, which could explain your different readings. QUOTE]

I have never noticed anything precipitating out of mine and just wondered what you had noticed out of yours. Maybe I am missing something here.

I saw it at King Ed's yesterday, both the pail and the 50 gal bags. Didn't look at the price though, but I did remember when I saw it that Ruth mentioned that it was pretty good. Maybe it's time to give it a try, since the outside packaging even mentions that the calcium and magnesium are sufficient