Dosing, as in a general what you put in the tank or specificly a Ca/Alk system?
There are all kinds of people that make all kinds of stuff to through in your tank. Most, believe in the less is more approach when it comes to adding things to the tank, as do I.
With that said, I will assume you are speaking of Alk/CA supplementation.
Your equipment needs will be determined by your tank need today and livestock choices. This demand will increase when calcium needing livestock such as clams, lots of LPS, and especially a tank dominate with SPS.
Currently you need is probably low and can get away with manually dosing by hand to completly understand how it works before shelling out the bucks for a doser, if you so choose that route. It is noted that there are a few ways of supplementation and all can be found in the links above.
Personaly I like the two-part system and have a doser. I dose B-ionic for the Alk and Ca, that includes trace elements as well to get me through to the next water change.
Water changes are another option for a low consumption tank as I am guessing yours is currently. Regular WCs are a reliable way to replenish Alk/Ca/traces. Eventually that replenishment with WCs will not keep up with demand and you will need to start supplementing.
Currently, I loose .5dkh in a day without dosing in my 75g with SPS and am forced to dose continually to keep it stable. On the other hand, my 24g nano has one small LPS and an Anenome and has been at the same value for weeks because its a low demand system and dont dose a thing.
Test your alk daily for a week and note the daily drop to help you decide if you need to supplement Alk/CA now or not......but Phyto and Top off can be dosed with a doser as well.
As far as future expansion.......what kind of tank is your "dream" tank? Use that to help you make choices now for equipment you can use then.
