W/C's and drop in SG
 

-just wondering what do you guys do when you have to do a big water change and you're SG drops, do you're fish and inverts such as corals,anemones, and crustaceans get really stressed with the decent drop in SG? -i just found a snail thats been dead in the same corner for a week and it gave out the most putrid smell i've ever encountered, and i'm guessing it could also be part of my cyano-outbreak thats plagueing my sand..:neutral:

I think most people here match SG BEFORE doing the change.

There should be no change in specific gravity when you do a water change.

i did test it before, it waz at 1.023 now it's at 1.021 if the hydrometer is right, but it was a bigger w/c at 20%

I have found hydrometers to not be very accurate.

: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

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

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..

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.

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

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.

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...

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

:lol: :lol: :lol: :lol:

his sig says "33-gallon mixed reef & freshwater cichlid tank." So it must be like a brackish tank.:mrgreen:

Its also a good idea to let the newly MIXED SALT WATER age for a day or so before adding it to your tank.

I have never heard of anyone adding fresh ro water to a marine tank when doing water changes. Just cause you have "always" done it that way doesnt make it right. No wonder your SG isnt stable.

Or its marine before the water change and then cichlid tank after the water change.:wink:

Hey could it be possible he has used the term Water change when he meant water top-up.

BV-Reefer were are you?

He's probably at school.

dunno. What Im confused about is him saying that using salt mixture would kick UP the SG... BV ya do know you can always use a little less salt in the mixture and match the SG with your existing tank? As in make your water change water 1.023 IF thats what your tank is at?

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

I give up

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

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.

It sounds like you need to pick a set point of specific gravity for your tank, and then read up on how best to maintain it. I'm not sure if your confused between topping off, and water changes, or if you just don't understand them out right.

Watch this ---> http://www.youtube.com/watch?v=kSTY346rros

In short, if your confused please ask. Many of us here are more the willing to help you out and get you pointed in the right direction.

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

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

I think the point people are trying to make here is that your logic, regarding water changes, thus far is fatally flawed.
I haven't seen a light bulb go off over your head with respect to your first couple of really ummmm.... unconventional posts concerning SG and water changes.
Read between the lines..... you could do a 100% water change and not change the SG.........

-ok ok i totally screwed up but it never caused absolutely any harm to any of my livestock so as you can imagine i never really made a big deal of it, but my w/c's are always small

Ergo, it's a top off......
Not a water change.......
Unless you're taking water out of the tank and replacing it with RO/DI water......
I don't even want to contemplate that gong show........

ok now you totally lost me...ergo?

therefore.......

The point of a water change is not to add fresh water its to add a new balanced source of sea water. Thats why people buy buckets of salt.

truckloads.... Aquacraft is retiring @ 55 because of me :mrgreen:

wow 4pg's..thats a new record for me..usually people give up at 2-3 :lol:, but seriously could this be the reason that i still have cyano bacteria, because i use fresh RO water?

well..... you really stepped into it this time
so to speak.......

let's clear something up here. By water change, do you mean you are siphoning out 5 gallons and replacing with a new 5 gallons? Or did you let 20% evaporate and now you topped it up? There is a big difference.

nono i siphoned out 5 gallons and put a clean 5 gallons in...just fresh water though

Right, there's the problem. As you are most probably aware by now, you need to replace the siphoned 5 gallons with saltwater at the same SG.

ok, I think this thread is done now...:mrgreen:

Ok, that is wrong. You need to add 5 gallons back of salt water of the same SG as you removed.
Now that we've cleared that up, you need to determine what the SG is now, using reliable equipment, and adjust if neccesary.