I was wandering what the paramaters need to be to create a snow storm from adding limewater? I have accidently done it a few times in fresh salt water. I don't want it to happen in my tank so what do I need to look for, pH, Cal, Alk levels?
Precipitates from Overdosing Limewater
When limewater is substantially overdosed, the transient precipitation of magnesium hydroxide from normal use may not be the only precipitate that forms. If the pH becomes elevated and stays that way long enough, calcium carbonate can precipitate throughout the water column. In such situations, the entire aquarium can become very cloudy, looking almost like skim milk (Figures 9 and 10). Such precipitation events have the beneficial effect of lowering the pH and alkalinity that were raised by the overdose, limiting the ongoing damage that takes place. In many cases, there is no apparent harm after a day or two, but in a few rare cases, when the overdose was especially extensive, a tank crash can occur, killing many organisms.
The following important points should help in dealing with a limewater overdose:
1. Don't panic! These overdoses do not usually cause a tank to crash.
2. The primary concern is pH. If the pH is 8.6 or lower, you need not do anything. If the pH is above 8.6, then reducing the pH is the priority. Direct addition of vinegar or soda water is a good way to accomplish this goal. Either one mL of distilled white vinegar, or six mL of soda water, per gallon of tank water will give an initial pH drop of about 0.3 pH units. Add either to a high flow area that is away from organisms (e.g., a sump).
3. Do not bother to measure calcium or alkalinity while the tank is cloudy. The solid calcium carbonate particles will dissolve in an alkalinity test, and all of the carbonate in them will be counted as if it were in solution and part of "alkalinity." The same may happen to some extent with calcium tests. Wait until the water clears, and at that point, alkalinity is more likely to be low than high. Calcium will likely be mostly unchanged.
4. The particles themselves will typically settle out and disappear from view over a period of 1-4 days. They do not appear to cause long term detrimental effects to tank organisms.
5. Water changes are not necessarily beneficial or needed in response to a limewater overdose.
Precipitates Where Limewater is Added
When limewater is added to seawater, a cloudiness can form almost immediately (similar to that in Figure 3, although not usually that intense). This initial cloudiness is magnesium hydroxide, Mg(OH)2, and it forms when the water's pH rises into the low to middle 10's. Theoretical and experimental reasons for believing this material to be Mg(OH)2 (and not magnesium carbonate or calcium carbonate, for example) are given later in this article. As the limewater is mixed in, the local pH around the particulates drops, and as soon as it drops below pH 10, the magnesium hydroxide dissolves.
If the limewater is not allowed to disperse rapidly enough, meaning that the pH does not drop fairly quickly, additional precipitates can form, especially calcium carbonate. Additionally, if the limewater drips onto surfaces in contact with seawater (such as the sides of a sump, Figure 4), bulk calcium carbonate can form on those surfaces. This precipitation takes place primarily because the limewater has pushed the CaCO3 supersaturation very high by converting much or all of the bicarbonate into carbonate. Since the precipitation of calcium carbonate can be slow to occur, rapid dispersal of the limewater doesn't lead to much or any precipitation of calcium carbonate. But if a region maintains high pH for long enough, calcium carbonate will precipitate. How long this process takes depends on the degree of supersaturation, but can be on the order of minutes to hours.
So the pH is the primary concern. Will adding Calcium chloride cause any problems?
Also, I have a fish only tank that I was using tap water to replace evaporated water. My tap water has a high Alk level. The Alkalinity has risen to 17KH. How can I safely lower it? It doesn't have any light and only two fish in the tank.
My main system has an Alk reading of 9KH and I use API test kits.