Can you explain in layman's terms how to use two-part properly?
For example, some people say you need to spread the doses out as evenly as possible over the 24h period so that the tank has a constantly stable supply. This is hard with a Jeboa dosing pump lol. But then I read once a day is enough.
Another point that is not clear to me is that some people say the point in two-part is that you can use each part individually according to consumption but then I read that two-part should never be dosed in unequal amounts which is it? And then you have a system like Redsea's where it's all dosed individually and has some crazy 3 to one ratio.
Nearly 20 years ago a company called E.S.V invented a product called B-ionic. This was a product that came in two bottles that replenished both calcium and alkalinity in their natural, ionic balanc…
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Depends on the dose and how concerned you are about changes in alk.
If alkalinity stability is the highest goal (it isn't always), the either spreading out the dosing through they daylight hours or automated dosing based on automatic measurement of alk is the way to go. The higher the daily alk dose, the more useful is spreading it out. At 0.5 dKH per day or less, it is not nearly as important as at 3 dKH per day.
This is my general advice for my DIY two/three part recipe:
An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com
Dosing Instructions
The dosing instructions are basically the same for each recipe, although any given aquarium will end up using about twice as much of recipe #2 as recipe #1 to add the same amount of calcium and alkalinity.
To initiate dosing, first adjust calcium and alkalinity to roughly their correct ranges. This may require a substantial dose of just the calcium part if calcium is low (e.g., below 380 ppm). I would suggest targeting calcium between 380 and 450 ppm, and alkalinity between 2.5 and 4 meq/L (7-11 dKH; 125-200 ppm calcium carbonate equivalents).
This calculator shows how much of what parts to add in order to boost one or both of the parameters by a certain amount:
Reef chemicals calculator
Then, once things seem roughly correct, select a starting daily dose for routine dosing. Here are some suggested starting doses, but the exact values do not matter much. The suggested doses apply to both recipes.
After a few days of dosing, note whether
alkalinity is low, high or on target. Only bother to test alkalinity, not calcium, during this period, because it is much more sensitive than calcium to over- or underdosing. Adjust the dose up or down as necessary to increase or decrease the alkalinity.
Once you have determined the proper dose, continue it until there is a substantial reason to adjust it (such as falling alkalinity as the corals increase in size). When adjusting the dose, raise or lower both of the recipe's parts together.
Resist the temptation to keep jiggering calcium and alkalinity independently. They will need occasional corrections, but that should not be the normal course of dosing unless there are substantial outside influences, such as water changes with a salt mix that does not match the tank's parameters or an error in making the mixes.
Check alkalinity fairly frequently to make sure the dosing continues at a suitable rate. Check it maybe once a week to once a month (or less as you get more experienced with the system and the tank). Check calcium once a month to once every few months to make sure it continues on track.
Remember to add an appropriate amount of Part 3 each time you finish adding a gallon of Parts 1 and 2 (or more often with smaller portions if the tank is small or you want to even out magnesium to a greater extent).