To keep your pH stable run a fuge at an opposite lighting schedule. No pH swings.
There is no better, only different.
The is an online magazine called "Advanced Aquarist". In the Feb 2003 edition there is an article called "How to Select a Calcium and Alkalinity Supplementation Scheme". It isn't perfect but explains the pros and cons of most of the commonly used methods of maintaining Alk and Calcium.
Here is a summary:
Very Small Reef Tanks
A very small tank (say, less than 10-20 gallons, especially those without a sump) will likely be served best by a system that does not involve the expenses, complications, and space requirements that come with reactors. Unless the calcification demand is very high, the costs associated with any of the simpler additives (the two-part systems, Salifert’s All in One, Tropic Marin’s Biocalcium) will probably not be prohibitive, and their ease of use makes them prime candidates. Without a sump, Biocalcium may be harder to add without solids getting onto organisms, so either of the other two types may be a better choice. Simple drip limewater is also a less expensive possibility for these types of systems, but is best used when a sump is available.
Fish Only or Fish Only + Live Rock Tanks
These systems have smaller demands for calcium and alkalinity, though rapid coralline algae growth on live rock can itself provide a significant demand. Since the demands are lower than typical reef tanks, the size tank that is best served by the simpler additives described in the previous section is greater. Maybe up to 55-90 gallons for a tank with a fair amount of live rock, and even larger with small amounts of live rock.
Large Reef Tanks
A large tank (say, more than 100 gallons) will likely be served best by a system that can deliver calcium and alkalinity at a reasonable unit price. Limewater and calcium carbonate/carbon dioxide reactors are probably the best choices, with limewater not sufficing for the higher calcium demand tanks due to its limitation based on evaporation rates. If you are handy, you can put the system together yourself, especially limewater from a reservoir. If you aren’t handy, then by all means buy a complete system.
Medium Tanks
These are the tanks that most beginners have, containing 30-90 gallons. The logical choices to pick from are more numerous than for the systems described above, and will come down to a series of different factors.
1. Does the tank have a sump where you can add high pH additives with less concern about nearby corals? If so, that’s a plus for limewater, Biocalcium, and the high pH two-part additives.
2. Do you have a good skimmer or other source of aeration? If so, that is a plus for using limewater (that needs to suck CO2 from the air) or a calcium carbonate/carbon dioxide reactor (that needs to blow off excess CO2). If not, using Biocalcium, All in One, or a two-part additive that has a small pH effect (like the bicarbonate B-ionic) may be better choices.
3. Is your home very tightly sealed, with possibly high indoor CO2? That is a plus for using limewater or a high ph two-part additive as they will counteract the tendency toward low pH.
4. Do you have space under or behind the tank for equipment? If so, that is a plus for limewater or CaCO3/CO2 reactors that need space and are typically unattractive. If not, that is a big plus for the simpler additives (two-part systems, All in One, Biocalcium).
5. Are you handy with complex systems? That is a plus for CaCO3/CO2 reactor systems and complicated auto top-off systems using limewater. If not, that is a plus for the simpler systems.
6. Are you very concerned about copper or phosphate in your tank? If so, pick limewater.
7. Are you going to leave the tank unattended for more than a few days? Pick a system with automatic delivery (many can be automated with the right selection of appropriate equipment, except Biocalcium).
8. Will the tank have a very high demand for calcium and alkalinity? That is, will it have lots of fast growing corals? If so, a CaCO3/CO2 reactor would likely be the best choice.
9. How much is cost an issue? For lowest cost, a cheap limewater drip will probably be best.
