Hello, So it took 3 doses of 45 mls alk to get it up to 7.8 which is right where I want it. I think it took 3 doses because the tank was consuming it over the 3 days . So now it's back to 15 mls per day. See if it stays there. This has b
een my problem for a long time, trying to keep it stable My tank wants somewhere between 12 & 15 mls. If it floats too high, I add few less mls. Then it drops too low .i increase the mls & it goes too high ! Drives me nuts ! LOL
Any way I see now it's better to dose all at once. Please wish me luck I can keep it between 7.6 & 8.3 .
Forgive me for a quick, Saturday morning without looking for your build thread and your tank's characteristics (size, inhabitants, etc...). One observation - a lot of respondents suggested that a quick return to "normal" levels was OK, and that's definitely correct if you've a fish-only, softie or hardy LPS tank. Those of us that keep SPS would probably not recommend doing that, though what you actually did (a roughly 1 dKH increase over 48 hours) should be OK.
On the "keeping alk stable" aspect. Besides a dosing pump, which does, of course, represent a substantial bit of $$$, there's a few different strategies to maintain alk at stable levels with manual dosing. In my case, I've never had a dosing pump on my 20 gallon nano, which has been running since 2004 with LPS/SPS. So it's definitely do-able.
1) Commit to a week of daily alk testing. You don't have to do it on this frequency once you get things dialed in, but it's necessary to nail down your consumption.
2) Log all of your measurements. I do this with a $2 old-fashioned blank journal that I picked up at Staples, but there's plenty of software solutions as well.
3) Get an accurate way to measure your solutions. If you make them yourself (I do), consider a $20 kitchen scale that has 1 gram resolution, and a container that you can precisely fill to a specified level, and that you use consistently every time you make the solutions. I use volumetric flasks, but that means another $50 or so - $30 for the magnetic stir plate and $20 for a couple of class-A volumetrics (one for alk, the other for Ca). It really doesn't matter that the solutions be made up really accurately, but it really does matter that they be made up
consistently, otherwise all of the work you're doing for alk measurements won't mean much.
4) Get an accurate way to dose your solutions. There's several choices here. In my case, since I'm a scientist with access to all sorts of lab equipment, I'd use a plastic 20 mL syringe to measure ~13 mL. Failing access to a syringe, you might consider a 25mL graduated cylinder off of
Amazon. Again, it really doesn't matter about accuracy here, but
precision does - it needs to be repeatable every time with a high level of confidence.
5) Once you have your tools ready (repeatable mixing and measuring containers), pick an alk and Ca dose in the middle of your usual range - say, 13 mL. Dose this consistently every single day during the week that you're doing the daily alkalinity measurements without fail, and do it at the same time every day +/- 1 hour. Do your alkalinity measurement at a consistent time as well, preferably at least an hour since your 2-part dosing. Really important -
do not alter the daily dose for this week, no matter what your test tells you.
6) Plot the alkalinity values on a graph - there's tons of on-line tools to do this, but I use Excel. You can also do it the old-fashioned way, with graph paper and a pencil. Either use the software to calculate a best-fit line to your data, or do it by eye on the graph paper. Measure the slope. If it's <0.05 dKH per day, that's about as good as you're going to get with hobbyist testing. If it's >0.05 dKH/day, you can make a small adjustment to your dose, and repeat the cycle. Presuming that your tank inhabitants don't change, and their growth is relatively stable, once you do this you can drop back to alkalinity tests twice per week.
Note that no hobbyist test kit has a precision of +/- 0.05 dKH, including ones that might actually read to this resolution, such as the Hanna. But that's the power of trend-line analysis; by repeating exactly the same thing (dosing and testing) every day for a week, you're averaging out the error, and getting a much more precise estimate of the consumption of the major trace elements.
