W/C's and drop in SG

[fishface]

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

[Jason McK]

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]

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...

[Aquattro]

ok, I gotta ask...is there anything alive in this tank??

[Rippin]

Originally Posted by reef_raf

ok, I gotta ask...is there anything alive in this tank??

[bv_reefer]

Originally Posted by reef_raf

ok, I gotta ask...is there anything alive in this tank??

-no theres nothing alive, cause i just love growing cyanobacteria and hair algae for fun..

[bv_reefer]

what ever all my fish and corals are growing great so no complaints so far, mind you i always do little water changes so the SG doesn't even go up or down really, just happened this time because i did a big w/c

[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

[Jason McK]

I give up

[Rippin]

Originally Posted by Jason McK

I give up

What matters is that you tried....


Ok, here it is -
Regardless if you are using a hydrometer or a refractometer:

1. When doing a water change, test your aquarium water's SG, then mix the replacement fresh water with salt to match this SG number. It does not matter if the water you are mixing the salt with is RO/DI or tap water - it will not make a difference in your SG levels. If you do this your SG will not fluctuate (by anything significant) during a water change.

2. When doing a water top-ff due to evaporation, DO NOT mix salt water for this, just use straight RO/DI fresh water and top off to the SAME level in the aquarium before the evaporation.

3. An SG reading between 1.023 to 1.025 is good. I would consider 1.021 too low.