PWC...a question....

[socalarsen]

Hey guys im doing my first partial water change, around 20%, of my 22 gal. my question is since my levels of gravity and salinity are at the top of thier suggested parameter, 1.024/32, should i replace the water with fresh, or with pre made salt from my lfs??? my gut feeling is fresh to level out the salinity/gravity, but you guys know far more than me at this point so any help would be much appreciated...happy friday!

 

[tecwzrd]

1.024 may or may not be correct depending on what you use to measure your sg. If it's a floating hydrometer or swing arm hydrometer I'd lower it to 1.020 (assuming it's not reef) to give yourself some room for error. If you use a refractometer then I'd keep it where it's at.

Main thing is if you remove SW you replace with SW and you top off evaporation with FW to maintain the sg since salt doesn't evaporate. Adding 4+ gal of FW would lower your sg too quickly.

You can use a lower sg mixture to lower your sg in the main. For 20% I'd recommend an sg of 1.018 which will lower your mains sg to around 1.022-1.023. After doing this a couple of times you will get your sg reading to 1.020.

Also FWIW fish can adjust to lower sg/ph much quicker than trying to adjust to a higher sg/ph. If you have inverts adjusting sg/ph should be done very slowly. To increase slowly (if needed) topping of your evaporation with SW is the easiest way IME.

Mix your SW with a ph for 24+ hours and match the temp/sg/ph to the main (unless trying to lower/increase in which case it should only be off slightly)

If your SW isn't properly mixed it can be caustic to fish/inverts and shock or kill them.

 

[socalarsen]

Well...it is a reef tank, and i get my water pre mixed from my lfs...

 

[tecwzrd]

What do you use to measure sg? Assuming the lfs is mixing it correctly there isn't much harm at leaving it where it's at. I wouldn't lower it personally.

 

[socalarsen]

i use the swinging arm meter, i cant remember the brand, but its got like the white pointer inside

 

[roka64]

I agree with the hydrometer vs. a refractometer.
My hydro showed 1.022
refracto 1.027

 

[tecwzrd]

Swing arm meters are known to not be as accurate as a refractometer for example but since you're getting your sw from the lfs does your reading match theres? Most people keep reefs at 1.024-1.026 so your fine if it's accurate. I assume you aren't having any issues with the tank currently.

 

[socalarsen]

no, in fact, i got my live rock (already cured) and live sand along with my salt water there at my lfs. put it all in and since about day 3 all parameter levels have been normal ammonia,0,nitrite,0,nitrate12.5mg/l,78degrees,ph,8. its about day 15 now and im going to add some cleaners to help with the diatom bloom. but i think i should change the filter pad and do a 20% water change since the top of the water is starting to collect a little white almost oily residue once it comes of the powerhead disruption...let me know what ya think, i should probably add some pics on here soon...

 

[tecwzrd]

No you aren't having any issues or No your sg reading doesn't match theirs? I assume you were answering if you had any issues but wanted to clarify.

Your levels are currently good but you still may not have enough bacteria to support fish yet even with cured lr. Cured lr bought from a lfs typically means there isn't anything decaying anymore but if your lfs didn't constantly provide an nh3 source then any bacteria within the lr would die out.

I'd do a fish less cycle before adding life to be sure. This article covers the steps.

 

[socalarsen]

I beleive they do have a good source of nh3 on the liverock, lfs is very well kept and provides very good products...