Hi Tom,
It's me again, hope you don't mind, just wanted to give you a quick update. I bought a mushroom coral, about 13 on one rock. I started using Coral Vital, half teaspoon per day. I also got a Ca test made by Red Sea Fish Pharm. Ca was 410 ppm and I've only had CaribSea aragonite in the tank about 6 months, maybe a little more, I'd have to check the log book. So good thanks again.
Robert Von Dullen
p.s. The store owner tried to talk me into using KW (kalkwasser). With Ca of 410 ppm, why should I!
Robert,
Your calcium level sounds good. Keep it simple. Your aragonite sand should continue to dissolve to replenish calcium used from the aquarium water for coralline algae and coral growth at reasonable rates as they grow or more are added. You seem to understand this already, but for the benefit of others who are also told they need to use all kinds of additives in excess, I'll expound.
Since you haven't been adding or overdosing KH (carbonate hardness/alkalinity) boosting additives (buffers), your calcium level SHOULD be over 400 ppm and the KH perhaps around 7 or 8 dKH, all on it's own, without adding KW (kalkwasser) or other calcium additives. The CaribSea aragonite sand does this as it slowly dissolves to provide this. I also hear from a lot of aquarists who listen to too many "cooks" and end up adding too many additives, and too much of them. This could ultimately lead to low calcium levels despite adding all the expensive calcium and buffering additives which are actually the cause of the calcium crash they unintentionally caused, all by themselves. Calcium crashes and dead aragonite sand are two common SELF INDUCED occurrences (yet normally unintentional) which many authors fail to address when recommending high KH levels. Even authors who address the more commonly recognized KH/calcium precipitation connection usually fail to address or even admit the existence of the KH/aragonite failure issue.
Robert, there is no mandatory need for you to use KW if it's all going that well. Although using KW can have some benefits, it is so easy to dose it wrong or use too much and end up with problems, especially if you would like to keep a simpler aquarium that uses aragonite sand to do the bulk or all of the buffering and calcium addition for you - the easy way. Boosting your KH can actually help accelerate uptake of calcium by coralline algae and corals for faster growth, especially the growth of coralline algae. It can sometimes help certain stony corals thrive where they may not in depressed KH and calcium conditions. But, when used in high doses it really can lead to precipitating calcium carbonate out of your aquarium water and forming calcite crystals on the aragonite sand grains, preventing them from dissolving as fast as they could otherwise.
KW tends to cause this calcium precipitation at a lower KH threshold than other common marine aquarium buffers do. Buffers come in many varieties, and all don't have the word "buffer" anywhere on the label. Two part calcium additives also buffer your water while adding calcium also, but they seem to have even more leeway before they cause precipitation of calcium to start, which leads to impairing or ruining your aragonite sand. Kalkreactors which dissolve aragonite or calcium carbonate sand in a chamber with CO2 seem to be the most lenient when it comes to causing this precipitation. You can push the KH higher with them than by other means before precipitation of calcium occurs. Even kalkreactors with their extra margin of safety CAN cause this problem too if you get carried away with pushing the KH too high. I wouldn't advise pushing your KH past perhaps 9 or 10 dKH via KW use, or past about 10 or 12 dKH with common buffers. I probably wouldn't push the KH much past 12 with two part calcium additives or even with a kalkreactor, just to be safe when it comes to calcium precipitation causing aragonite failure. Albert Thiel has published more detailed information on this variable precipitation phenomenon on his web site. If your aragonite sand actually clumps you will know for sure that major calcium precipitation has happened. Using wild aragonite live sand or even older "dirtier" tank-raised aragonite live sand will often eliminate this clumping problem altogether, despite the fact that calcium is still precipitating from the water with high KH. Even in these cases, the aragonite sand fails anyway, even with no clumping. Don't EVER count on aragonite sand clumping to tell you when to cut back on the addition of KH raising additives. The sand CAN be ruined well before any sand clumping ever shows up. I've seen it happen and have also heard enough cases from others. For some reason people think they can put an inch thick layer of wild aragonite live sand over the top of several inches of less expensive CaribSea aragonite sand and that since this keeps all of the sand from clumping that the sand is ALSO safe from losing it's dissolving or buffering power - NOT SO!
A common buffer abuse scenario is as follows. A hobbyist adds KW or buffer or a two part calcium additive or even SeaChem Reef Builder which also fits into the buffer category even though many people think it is somehow exempt since it does not raise the KH quickly. Initially you may be able to push the calcium and KH levels up together, but as the KH is boosted further, the calcium level drops, and as KH is pushed even higher (perhaps to 18 or 20 dKH) calcium precipitates out of the water. The water's calcium level plunges, sometimes diving to about 200 ppm as the KH rises. The aquarist now lets up on the dosage of the additive or multiple additives and waits for the aragonite sand to kick in again and raise the calcium level back over 400 on its own as it is supposed to. If the aquarium doesn't have extreme calcium demand from an overload, perhaps of fast growing stony coral and coralline algae, then the aragonite sand can keep dissolving to replenish calcium and keep levels over 400 ppm.
KW and the other additives do have some good use though, but be careful if you ever decide to use them. Overdosing is common, remember the old adage, "If a little bit is good then a lot must be really good!" They can accelerate coralline growth quite well. KW especially seems to have this effect, but keep it light or just don't mess with it at all. A can of pickling lime (hydrated lime - calcium hydroxide) for under $2 at the grocery store works fine. But, if your nighttime pH does not drop too low, then it really won't help much in this important category anyway. Skip it if your aquarium is doing fine.
Rick Greenfield of CaribSea recommends not using KW unless it is really needed to raise low nighttime pH, and then only in modest quantities and preferably with a doser so you don't end up overdosing and accidentally precipitating calcium and impairing the sand. Some KW users have used hospital type IV bags or just the dripper hooked up to a larger container if needed. They regulate the drip so that it takes all night to drip in the amount of KW to replace evaporated tank water. I would use only about ½ tsp (or less) of dry KW powder per gallon of RO water to be dripped into the tank rather than the much higher rates often being recommended (such as one tsp to two TBSP. per gallon of top off water!). People who have had coralline stripping in their tanks (often from certain hermit crabs which "don't ever" eat coralline
It's easy to get carried away with KW or other KH boosting additives and lose the benefit of your aragonite sand. It usually takes a little while, and sometimes even a few months, to get the maximum dissolution rate going with your new tank's aragonite sand bed. This can vary from tank to tank. It appears that bacteria must develop in the sand bed and some nutrients settle within the sand to help achieve the maximum dissolution rate as it is used by coralline, coral and other calcium users in your aquarium. By the way, aragonite sand is a big time and money saver for fish-only tanks also since your fish need buffered water with a good pH level also.
Tanks-
Tom Miller