Here's a few good questions that were raised over PM. I'm sure other people have the same questions, so I figured I'd post the question & response in here,
ruppertb said:
so this is totally off topic but i didnt want to jack the thread, i see you keep sps and might be able to help me.
my ph is always low like 7.8 or 8, and my alk is super low like 6 or 7.
so i have been over the past week and a half raising my alk with baked baking soda. So last night before i dosed the last bit i had and thought it was supposed to be where i wanted it around 10 or 11 it tested out at 8.so i added it and then tested it at about nooon today and it has gone down again to like 6-7, any ideas as to why.
One piece of information that you didn't mention that is important in this discussion is your current magnesium level. Magnesium is necessary to maintain levels of calcium & alkalinity within an aquarium. You should strive to keep your Mg levels between 1300-1600 ppm.
As far as testing alk, you should always wait about an hour after dosing to test your parameters so that it can be spread evenly throughout the system. Your alk will drop because it is used to precipitate calcium as a skeleton is formed by the corals. In a way, it's a good thing that it's being depleted because that indicates that your corals are growing. Alkalinity is usually depleted at about a 2:1 ratio with calcium, but in short term situations, that ratio may be slightly skewed. You may be currently depleting at about a 3:1 ratio, but that doesn't mean that you should withold calcium dosing because it will eventually catch up to a normal 2:1 balance. (Randy's 2-part recipe compensates for this ratio by making the alk roughly 2x stronger than the calcium solution) Calcium & alk have an inverse relationship, so if you raise calcium, your alk will drop and if you raise alk, your calcium will drop until they are in balance.
I would ramp up your alk dosing slightly to get your parameters where you want them. Your calcium levels will naturally fall as alk goes up, but not all that significantly. Remember, the most important part of alk is stability, don't feel that you need to strive for a dKH of 11. I run my tank at 8 dKH and have never gone any higher. Once you get levels where you want them, don't dose anything for a day and then retest. Use a reef calculator to find out approximately how much two part you'll need to reach your desired levels again and bring the levels back up to where you want them. Whatever you need to add will be your current daily demand for 2 part. However, if your alk or calcium drops significantly over that 24 hour period, (more than 50 ppm of calcium or more than 1.4dKH {0.5 meq/l}) then you will need to dose more than once per day to prevent swings in calcium & alk that will be rough on your corals. If you have frags at this point, then you shouldn't have that problem, but as your corals grow, you may need to make that change. Also, your demand will change as corals grow, so you will need to retest every so often once you have your dosing dialed in to see if your dosing needs to be increased.
Something you may want to look into is kalkwasser dosing to help stabilize your Ca/Alk and also raise your pH a bit. This can be done by dripping a kalk solution, using a kalk reactor, or adding kalk to your ATO reservoir. Other ways to raise your pH include adding an airstone, providing fresh air for your tank, and running a light over your sump on a reverse light cycle. By adding an air stone in your sump, the bubbles bond with CO2 within the water column and allow them to escape, thus raising your pH. Introducing fresh air to your system will also raise pH, and this can be achieved by just opening a window or running the air line from your skimmer outside to inject fresh air. In case you haen't noticed, pH will fluctuate throughout the day and is lowest when the lights are out. By adding a light to the sump on a reverse light cycle (On when your reef lighting is off), it will help prevent a drop in your pH, stabilizing it.
