Question about Water Change

[luntiz]

I just completed a 4gallon water change in my 40gallon tank and i have a few questions:

When is the recommended time for a water change (I had my tank for 3 weeks prior to today's water change. Today was my first ever water change)?

How much water should be replaced (As mentioned above, I did a 4gallon water change)?

Should I test the "new" water to try to match everything as close as possible? Will there be any negative impacts on my livestock? (The water I used was from the LFS. Their salinity was lower than my tank salinity)

How about the temp? (My tank temp is 80 and their water was at 78 )

Thanks in advance!

 

[mhaynes01]

if you add the water in slowly it will be fine

 

[Anemoneman]

USUALLY Try to match the salinity, pH and temperature to minimize impacts to the livestock. Failure to do so likely won't kill anything but will cause some corals to retract for a while and may stress some fish. 10% isn't enough to worry about though. I would just pour it in.