Confused About Chemistry

[Danzig]

I dont have my tank setup yet, but i have almost everything i need, with some things coming in the mail. I have a 72 gallon bowfront tank with a 20 gallon sump, i want to start off with live rock and soft corals and easy fish. According to this thread,http://www.reefcentral.com/forums/showthread.php?t=1805742 , under the "basic measuring needs for all saltwater tanks " (which is what i want to stick with for now until i learn more) i need to measure my alkalinity. Doesnt a PH meter measure alkalinity? Because anything over 7.0 is alkaline and i should keep it between 7.8-8.2 for saltwater correct?

To avoid confusion, answer the above question first, then the below question please.

Also, under the "kits for reed tanks with stony corals or coralline" it says i need to maintain calc and magnesium. I will not be having stony corals, but i will have coralline because of my Live rock and will start with soft corals because they are easier some say and require less light. So im just wondering what happens if i dont maintain calc.. and it seems really complicated if i have to add calc then worry about my alk changing and vice versa. This also goes for phosphate as well.

Basic measuring needs needed for all marine tanks:
ammonia
SG
temperature
alkalinity

Kits for reef tanks with stony corals or coralline:
calcium
magnesium
Kits sometimes useful for trouble-shooting or preparing reef tanks with stony

corals or coralline:
phosphate
nitrate
nitrite
pH

Im really confused about all this chemistry stuff and i really want to keep the gadgets to a minimum because of budget reasons and my beginner status as a reefer.

[Waddleboy]

I am new, but i can answer the basics of the chemistry for you. Alkalinity and pH are completely different. pH is a measure of the H+ ion dissolved in the solution. Your typical acid base. That should be kept in your range stated. Alkalinity is a measure of the buffering ability of your system to neutralize acids. This is so your pH does not change drastically. Alkalinity sound like alkaline which is a basic solution but they are not the same. From what i have read alkalinity should be maintained between 8-12. As for your second question i dont really know what your asking but as i am knew i probably wouldnt be able to answer it sorry... but if your asking will adding minerals will affect alkalinity the simple answer is yes (at least in real life so i imagine that would apply to aquariums) please anyone correct me if i am wrong

[Palting]

No, pH and alkalinity are two different measures. Alkalinty measures the buffering capacity of the substance, it's ability to resist pH change, and the pH measures the base to acid ratio. It's a simplified answer, but I suppose it will do for reef keeping purposes.

If you want to give empasis to one question, then ask that question only, and start another thread for the other questions.

As to the other questions, best way to answer them is to give you the whole picture as it pertains to saltwater chemistry. Too much for one post. So, here are somme links that may help you answer your own questions. HTH!!

http://reefkeeping.com/issues/2006-06/rhf/index.php
http://reefkeeping.com/issues/2006-02/rhf/index.php

And the mother of all links, everything you always wanted to know about reefkeeping chemistry:
http://reefkeeping.com/issues/subject/chemistry.php

Ok. So now, to simplify everything. If you use a quality salt, like Instant Ocean or IO ReefCrystals, and if you keep your SG at 1.0268, and if you do regular water changes, you will likely not need any calcium or alk supplementation for a while. Even if you have coraline or soft corals. The salt and the water changes will maintain yout calcium, alk, pH, magnesium probaly until your tank is a year old, possibly even longer. Start dosing calc only when you start noticing a drop in calc or alk, and use 2 part, which gives you balanced doses of calcium and alk.

As to phosphate, you don't want any. You don't dose it, you want to keep it out, and if you detect any, you take it out. But, that's another thread altogether.

HTH, and GL!!

[disc1]

Waddleboy is right on with the alkalinity terms. Alkalinity represents the buffering capacity of the water and it depends on a wide range of things that in the reef aquarium basically boils down to carbonate and borate.

By buffering capacity, I mean how resistant a solution is to a change in pH. If I add 1 mL of concentrated HCl to a liter of pure water the pH will fall drastically to 2 or less. If I do the same to some seawater with a high alkalinity, the pH might not fall by more than a point.

As far as how calcium and magnesium affect alkalinity, that can be a complex issue. Calcium and carbonate are super-saturated in seawater. That means there is more there than the seawater should theoretically hold. It should precipitate out. Magnesium interferes with that process and helps keep it in solution. The details are complicated, but the basic concept is simple. Get alkalinity stable, then get calcium right, then occasionally check up on magnesium. If alkalinity or calcium start to act funny, the first suspect should be magnesium.

And when all else fails, stop by the chemistry forum and ask. They don't bite in there. Matter of fact, there is a sticky in there with a whole bunch of articles that explain the very things you want to know.

Here's a link:
http://archive.reefcentral.com/forums/showthread.php?s=&threadid=102605