W/C's and drop in SG

bv_reefer · #1 09-06-2007, 05:27 AM

:ya thats what i thought to, but i tryed 2 times with the same reading, 1.019!
i bumped it back up to ~1.021 for now

Captainhemo · #2 09-06-2007, 07:06 AM

Really give those hydrometeres a good couple of bumps and make sure it is sitting on a level countertoop when you read both when you are checking the tank and when checking you new water before adding it. Just holding the hydrometer at the slightest angle can "bind" the float/pointer and give you an incorrect reading.
As long as your nrew water is at or above the SG of the tank, there is NOWAY the SG can come out lower

bv_reefer · #3 09-06-2007, 07:22 AM

well i just put RO water, i didn't add salt because it was already at 1.023 so a 20% w/c with salt replacement would've kicked up to 1.025, i've never used saltwater as replacement water for a water change..

Pescador · #4 09-06-2007, 07:33 AM

A water change is different from topping up evaporation.
Top-up with fresh water because salt doesn't evaporate but water changes are done with pre-made salt water at the right SG and temperature.
You drain a % from the tank and add the same amount of new water.
Try to make any SG changes gradually.

fishface · #5 09-06-2007, 03:25 PM

get a refractometer. they're more expensive than hydrometer but one of the best investments for accuracy.

Jason McK · #6 09-06-2007, 04:40 PM

A 20% water change with out and salt is insane. If your hydrometer read 1.023 without adding any salt I would have thrown the Hydrometer in the garbage and stopped the water change.

Aquattro · #7 09-06-2007, 05:15 PM

you HAVE to add salt to your water change, that's the whole point!! You add water that is the same SG as the tank. And BTW, there is no way RO water was anything higher than SG of 1.000. That is pure water. Your equipment is either way off, or you're doing something terribly wrong...

bv_reefer · #8 09-07-2007, 12:31 AM

ya i've been looking into a used refractometer but honestly i don't think that SG has to be super accurate for coral health as long as it's consistent

Jason McK · #9 09-07-2007, 01:38 AM

I give up

Aquattro · #10 09-07-2007, 02:04 AM

Quote:

Originally Posted by bv_reefer

ya i've been looking into a used refractometer but honestly i don't think that SG has to be super accurate for coral health as long as it's consistent

Well, it has to be consistently accurate. Now adding straight RO to your tank kinda drifts away from this theory, dontcha think?