Confused over KH levels

[J-P]

I hope this is a simple question. I have read that Crystal Red Shrimp (CRS) are best maintained wit the following perams:
pH 6 - 7, GH 5 - 15, KH 0 - 2

That last number confuses me. AFAIK a KH level that low depletes the beneficial bacteria in the tank and would cause PH swings.

I have read http://www.americanaquariumproducts.com/AquariumKH.html and it is fairly straight forward.

So... how could such a low KH level support a tank full of shrimp?

[RTR]

Low KH levels give soft acid water, as you know. I cannot breed these shrimp at all well with my water unmodified. Therefore I have no useful experience in keeping them - only poor results. I can confirm that they do not like my KH 7-9 water at all. Colonies will die out rather than increasing.

Low KH/pH water only requires care in avoiding metabolite build-up (that includes over-feeding or over-stocking, absolutely) - which can pH crash the tank. Extreme low pH is not very hospitable to out standard nitrification bacteria, and can/will reduce their replication rate.

The only times I use soft acid water is in conditioning and breeding tanks for blackwater fish which require calcium/magnesium free water, and I cheat on those during conditioning by supplementing with bicarbonates lacking those minerals, but giving me workable and sustainable pH levels. I have never tried using such water for those shrimp - there are more shrimp than I care to keep which do just fine in my water, so I use those.

[J-P]

That's what I though for the most part. It seems like an overly delicate balancing act. As much as I and another member are interested in these, I am not certain I want to go through that much trouble. The odd thing is that the company supplying these has mineral additives that, I thought, would raise the KH, including calcium (although they claim it does not)

[RTR]

Calcium will raise the GH, not the KH. It depends on what the cation is attached to the calcium before it is dissolved as to whether or not it will hit the KH - calcium chloride would not increase KH, calcium carbonate or bicarbonate would.

[J-P]

ahhhh....now I understand

[RTR]

No sweat. That is how so many folk are convinced that GH and KH have to be linked - they are related in most natural waters - calcium carbonates and bicarbonates are everywhere, almost. But that does not mean that they MUST be linked. When we are reconstituting RO or RODI for special needs critters, we can play games Mother Nature would not touch.

The Crystal Reds forebears must have been from a fairly special ecological niche...