HiC2 pool, roughly speaking is a pool with CYA levels around 150ppm, that is operated (per the Best Guess chart) with chlorine normals between 8 & 15 ppm, and shock doses to 25 ppm.

The benefits are:
1. your overall chlorine loss drops.
2. you have a large chlorine 'reservoir' in the pool, so an 'event', like a party of peeing people, doesn't mess up the pool.
3. if you dose manually, you maintain your pool with only 1 or 2 doses of chlorine per week, cutting down on maintenance time.

The problems are:
1. You must use FAS-DPD testing for chlorine-- you can NOT use DPD tablet testing. (You can use OTO to get a rough measurement of chlorine)
2. You must use Taylor's phenol red for pH testing AND use a special dilution (1/2 pool water + 1/2 distilled water -- available at Walmart) when you test.
3. If you let algae get started, you must either (a) raise your chlorine to VERY high levels, possibly as high as 50 ppm, (b) use an algaecide, (c) use sodium bromide -- but let me give you instructions! If you use very high chlorine, it will take weeks to drop. Algaecides either stain OR don't play well with chlorine. So . . . I recommend bromide (CAREFULLY!) + borates.
4. If you tell anyone what you are doing, they will think you are crazy.

The history behind this is what chlorine 'shooters' -- they service pools by injecting chlorine gas directly into the pool weekly -- have been doing for 40+ years. I've known about this for years. In fact, knowing about it was one of the key triggers for the thinking and work that led to the Best Guess chart. But, there were some pieces to the puzzle of how individual pool owners could do this, that I only worked out in the last year.

Richard (Chem_Geek) has reservations about this, because of the high chlorine levels to kill algae. But, the answer is two-fold:

1. Use of borates at 50 - 70 ppm will reduce the pool's 'friendliness' to algae.
2. Keeping the borates high, and the alkalinity (TA) low will do the same, because the CA (carbonate alkalinity - carbon dioxide for plant growth) will also be low.
3. If you keep your chlorine levels up, and maintain your pool, algae is unlikely.
4. Careful application of sodium bromide -- IF algae occurs -- will introduce an unstabilized halogen residual, that will tend to be effective against algae at levels of 0.5ppm bromine or LESS.
5. In OUTDOOR pools, where the chlorine levels is several multiples of the bromide / bromine levels, the bromide will be converted to inactive (in a pool sense) bromate in a fairly short period, avoiding the problems described in my Once a Bromine Pool page.

The bottom line is, a HiC2 pool is easier and cheaper, but you have to prepare, and learn how to do it BEFORE you start. This means:

1. Having a K2006 (or equiv) and a K1000 (OTO / Taylor phenol red on hand
2. Maintaining 50+ ppm borate levels in your pool
3. Having sodium bromide on hand, AND having pre-calculated doses for your pool.
4. Having polyquat on hand (as a final backup!)

Phosphate removers could be a final backup, except that they are likely to rapidly go off the market. They use lanthanum, which is one of the 'rare' earths for which China has gained a state mining and production monopoly. I've been told re-packager pricing for lanthanum chloride has gone from $1.20/lb in 2010 to $20+/lb in 2011, to unavailable in 2012!