I totally get that. For part of 2008, I was getting my magnesium level up, and until it was up, I couldn't get my alk & calcium high enough. After my magnesium level was at 1400, my calcium and alk levels were good. After I bought my largest clam, my magnesium levels stayed the same, calcium levels went in the high 400's, and alk dropped below acceptable levels. By adding alk, my alk comes back into an acceptable level, my calcium dropps into the low 400's, and my magnesium stays the same. Should I be adding calcium as well, even though what I am doing is keeping all levels in the acceptable levels?

Personally, I'd use kalk. It keeps Ca and alk at proper levels, baking soda should be used more of a fix, IMO. I only use it if I notice a sharp drop in my alk. Otherwise, kalk. You wouldn't need it full strength either, and likely wouldn't need to mix it once stirred.

I think the standard advice would be to add Alk supplement only until you achieved "balanced Ca/Alk"...What you consider to be balanced is maybe a bit subjective... Let's say it is around 400-440 Ca...and about 8-9DKH.

Once you have that, you should maintain it with a balanced additive (like A/B, Kalk, Ca Reactor). Then use this balanced additive to maintain these levels. A dropping Alk level serves largely as an indicator that you are not replacing BOTH...even though the Ca level appears to be holding.

To quote Holmes-Farley..."The "mechanism" arises in the simple fact that alkalinity rises and falls much faster than does calcium because seawater has a much bigger reservoir of calcium than it does alkalinity."

A good recommended read:
http://reefkeeping.com/issues/2004-12/rhf/index.php

You use tap water rather than RO right? I imagine Ponoka has fairly hard water like the rest of the province so every time you do a top up with your tap water you are adding a fair amount of calcium but not very much alkalinity. If you use something like Kalkwasser in your top up it won't fix the problem as you are adding more or less balanced amounts of calcium and alkalinity to water that already has a lot of calcium. Boosting only alk in the top up by adding something like sodium carbonate (your baked baking soda) makes you top up into a balanced calcium / alk additive as well.

The easy way to go forward is to get yourself an auto top off of some kind and supplement the ATO water with Alk.

Any recommendations on a good ATO? I see Tunze carries one, but it appears to come with a tank to hold water, and I'm going to have to make a custom one, as I don't have a lot of space to put it.

If you want to automate your tank more, I would also suggest you get an ATO and add your Alk to the reservoir. You will need to have a reservoir for the ATO. The size depends on what you want, but I would suggest something at least 15% of your total system's volume or you will end up having to fill the reservoir too often.

I can't imagine what you have under your tank that is taking up all the space when you only have a 55g sump and no reactors?? Is it poor space management? Maybe you can try to do a renovation under there, and get some more space opened up?

Is it true that you are using tap water? If so, that may be your answer as to why you're needing to add alk, but not calcium as midgetwaiter suggested. If you are in fact using RO/DI water then you need to look into the alk usage futher.

I use RO water, not tap water, so I don't think that is the problem. When I was using tap water over 2 years ago, I was having issues with phosphates, so switched.
A main issue with space is I have to set up a fan underneath in the summer to keep the temperature down, so that chews up a lot of the space. I suppose I could put the fan on top of the reservoir, rather than a stand, opening that up, and also screwing in my MH ballast's to the wall.

Ok, so you're using RO water. Do you test the TDS of your product water regularly? If so, what is it at? If not, it is $28 well spent. An RO unit is really not complete without a TDS meter. What salt are you using? What products are you using for magnesium and calcium? What are your magnesium and calcium sitting at? Take a quick glace through Myka's Guide to Calcium, Alkalinity, Magnesium... in my signature, maybe you can pick up a missing link or something. It's an easy read, don't worry! ;)

Another option for fans is to cut out a hole in each end of your stand and install fans one in each direction that mount right into the holes. This way you get really good airflow through the stand, not just in the stand, plus they don't take up any room at all. PFO ($40 each I think) and IceCap ($90 I think, but variable speed) make good ones. I'm sure you could find them in a hardware store too for much less, just look for ones with as little metal on them as possible to lessen rusting.

If I read correctly, that you have the ballasts under the tank, maybe if you moved them out, the temperature would not go up so high in the summer

Presently, I am not testing my RO water regularly. I use Bio Sea Marinemix salt. My magnesium is at 1410, and my calcium is at 440. I am not real keen on cutting holes in my stand, but it may be an option that I have to consider. I'm curious is cutting holes in the canopy wouldn't be the better solution though, as this is where the heat is generated.