Unexpected shrimp deaths

[Lee04]

I have a 10 gallon which has been set up since Sept 2011. Every test I can do checks out ok, except the pH. I'm not sure which method of pH testing I should trust because of the conflicting results. I am inclined to trust the liquid API low ph. What do you think?

pH:
-Measured by api low ph: 7.6
-Measured by api high ph: 7.4 (< result was a bit lighter than 7.4, actually)
-Measured by digital test: 7.0

Other Stats:
Nitrate/Nitrite: 0
Ammonia: 0
TDS: 213 (Tap & Distilled, dechlor Prime)
kH/gH: ?

The shrimp was a fire red, which was about 4-6 months old. The rest seem healthy.
Shrimp have been molting successfully, even the smallest (1-3 mm).
I have paintball CO2 running at 1 bps. The pH seems to be fluctuating, yesterday it was 6.5-6.6 according to digital test.
Could the CO2 be influencing, or perhaps digital pH is not that accurate?

Thank you for your help!

[CatB]

it might be the kH/gH if you don't know those. or sometimes shrimp just...die. it happens to everyone :P

[diwu13]

A fluctuation of +/- 1 pH won't cause neocaridina to die, especially something as hardy as RCS.

Was it only that ONE shrimp that died? Could be of old age. How many shrimp are in the tank?

[Lee04]

Yep, it was only one. I found it's tail. There are 11 shrimp in the tank.

[diwu13]

It's probably due to old age then.

[Lee04]

How long do fire reds live? I heard it was 12 to 18 months, but the ones I have are only 4 to 6.

[Bananariot]

4-6 months after you bought it or were they babies that grew up.

[Lee04]

I bought them when they were 4-6 months old. I've had them about a month.

[diwu13]

How did you know they were 4-6months old? After like 5 months they just all look the same to me lol?

[Lee04]

I asked seller

[lauraleellbp]

Are you checking your CO2 levels throughout the day? Especially about an hour after lights off?

[Lee04]

The co2 checker has been blue 24/7 because of all the water movement. I'm going to move it to another tank since it's not really needed in this one.
Everyone else seems unaffected, so it might have been an affliction on the individual.

[diwu13]

Hm... isn't a blue CO2 level indicate high levels of concentration? Not sure since I don't use CO2 myself. I know most people with shrimp keep levels at like lime-green.

[Lee04]

Blue is low co2, lime-green is what you want in most cases, and yellow is too high

[Bananariot]

So how long did you have the shrimp before it died?