[Chemical Treatment For (very) Small Temporary Pool]

The main issues you need to be concerned about are filtration and chemical balance. You should run the filter as much as possible. The chemicals that are most important are chlorine, pH and alkalinity. You can purchase a cheap test kit that will do these tests at most pool, hardware or general stores. You should maintain about 2 to 4 ppm of chlorine, a pH of about 7.3 to 7.7 and an alkalinity of about 70 to 120. You can use bleach for your chlorine. Be sure to use only original unscented bleach such as regular Clorox. Use about 2 ounces of bleach to provide 1 ppm of chlorine. You can use baking soda to raise your pH or alkalinity. Use about 2.5 ounces of baking soda to raise your alkalinity by 10 ppm. You can use muriatic acid to lower pH or alkalinity. Use about 2.5 ounces of muriatic acid to lower total alkalinity by 10 ppm. You can buy a quart of muriatic acid at any hardware store. Be very careful with acid as it is very dangerous. Pour the required amount of acid into a plastic cup (not Styrofoam or paper) and then pour it into the pool. Only add one chemical at a time. After adding any chemical wait several hours and retest all chemicals before adding the next chemical. You should also buy a skimmer net and brush to remove debris and keep the bottom brushed.

[Stabilizer Stain]

The liability issue is with the person who put the stabilizer in incorrectly. Why was the stabilizer just dumped into the pool? What are the directions that are printed on the container that the stabilizer came in? How long did the stabilizer sit in one place? Are you 100% sure that it was stabilizer that was added? What other chemicals were added, and how, after the stabilizer was added?

[What Kind Of Shock Do You Think Is Better?]

I try to avoid using pH up. As you noted, using liquid chlorine will usually keep the pH from going too low. If I feel like I need to raise the pH, I will usually use baking soda (sodium bicarbonate) rather than sodium carbonate.

Sodium bicarbonate goes in very cleanly. Yes, I know that it is for raising the alkalinity, but if you add just the right amount, the pH will almost always go exactly where you want it. If I need to avoid raising the alkalinity, then I will use PH up. I find that with limiting the amount of sodium carbonate to a maximum of one pound per five gallons of water and mixing well, the cloudiness can be minimized.

The heater and salt cell should be turned off whenever adding such chemicals, and left off until the cloudiness is fully gone.

Part of my concern is that the high concentrations of calcium could combine with the hydroxides created by the salt cell to form calcium hydroxide and then combining with carbon dioxide to form more calcium carbonate.

I will sometimes dilute liquid chlorine to about 1 to 2% before adding it to a pool. This mitigates the risks by reducing the density and the concentration. Pouring undiluted bleach or liquid chlorine slowly into the flow from a strong return is also good.

I do not generally like adding bleach or liquid chlorine through the skimmer. It is OK if there is no heater or other metal in the filtration system, there is a sand filter and wall returns. The high chlorine will have a detrimental effect on a copper heat exchanger, salt cell plates, brass gate valves, the fabric in a DE or cartridge filter and other such elements. If the pool is plaster with floor returns, the chlorine could cause metals in the water to plate out on the floor around the inlets.

I have never had any problems adding cyanuric acid through the skimmer. How low do you think the pH goes when the cyanuric acid is dissolving?

I can get calcium chloride to fully dissolve to a clear liquid in a bucket before adding by mixing a maximum of two pounds per five gallons of water and by only getting the highest purity. There is never any undissolved solute. I strictly avoid the low quality 77% stuff.

[What Kind Of Shock Do You Think Is Better?]

Furthermore, if you do vacuum residue/undissolved cal-hypo, there will be a large spike in the concentration of calcium and chlorine inside the filtration system, which is not good for your system.

[What Kind Of Shock Do You Think Is Better?]

Even with pre-dissolving the cal-hypo in a bucket and an unsaturated condition, there is still residue and clouding. The undissolved portion can bleach liners or dark plaster. If the undissolved cal-hypo hits white plaster when the ph and/or the alkalinity are too low, it can cause a black or gray stain.

It is unsafe to swim in the pool until all of the cloudiness is gone. The cloudiness can act as a precipitating agent for calcium carbonate scale to form in heaters where elevated temperatures alter the SI or salt cells where the high pH caused by the hydrogen being removed and the carbon dioxide being agitated out of solution also increases the local S.I.

Dissolving cal-hypo in a bucket is messy, dangerous and tedious.

Plaster pools should always be kept near saturation to protect the plaster. Any negativity in the SI always damages the plaster; and plaster is far more difficult to redo than most people realize.

I cannot think of one single advantage that cal-hypo has over liquid. Even if there is a slight price advantage, it doesn't overcome the serious problems of using cal-hypo. As far as weight, bleach is so available it offsets any density advantage.

Calcium chloride should be added separately if needed.

In addition, if the cal-hypo is 73%, then there are still 27% of mystery garbage chemicals being added to the water.

[Best Pool Epoxy Brand?]

Zeron used to be very good until they started worrying about the environmental impact of the VOCs emitted during the drying process. VOCs (volatile organic compounds) are solvents that are released into the air as the paint dries. Now, there is no paint that I think is worth using.

[What Kind Of Shock Do You Think Is Better?]

Calcium Hypochlorite is a bad choice. It never fully dissolves; and some of the powder falls to the floor. The powder that falls to the floor can cause stains or bleaching. Calcium hypochlorite takes too long to dissolve; and it clouds the water. The residue that ends up on the floor will re-cloud your water when you vacuum or brush.

Sodium hypochlorite (Liquid chlorine or bleach) goes in clean with no residue and very little waiting if you don't over chlorinate. Even for pools that need calcium, it is far better to use the liquid chlorine and add the calcium separately.

["i've Never Seen This Before"]

A water softener company can do this. Tell them that you need to fill your pool. Tell them how many gallons and what the calcium level is in the fill water. They will come out and set up the number of tanks needed to do this. After the pool is full, they will return and remove the tanks. The tanks will be rented for the time required to fill the pool. They will not be permanently installed.

[Every Day?]

"If that's the case then It may be worth the extra money with Baquacil."

I strongly advise against Baquacil.

[Problems With Br]

I would highly recommend that you drain and refill the hot tub. Forget about bromine. Use bleach to maintain a sanitizer level as needed. The green is probably copper being corroded from the heat exchanger in the heater. Monitor the heater closely for any leaks. You can use trichlor in the feeder to provide a low continuous feed of chlorine, but be sure to monitor the cyanuric acid (stabilizer) levels carefully.

Is the Hot Tub plaster, tile, or what?

What temperature do you keep the Hot tub at?

["i've Never Seen This Before"]

You are right about this being temperature dependant. As the temperature increases, carbon dioxide is forced out, which reduces the water's ability to hold calcium. Warmer water cannot hold as much calcium as colder water. This is counter intuitive because most people are familiar with warmer water being able to dissolve more solute.

I think that the best solution is to contact a water softener company to see about removing the calcium. You can divert part of the filtered water through a softener system to remove the calcium. You can install a softener system for the fill water as well.

The fact that you are using a salt system may interfere with a water softener being used to remove calcium from your pool water. You may have to do a partial drain, and refill with softened water.