I do use a hydrometer when mixing water. Before i even start adding salt, i already know about how many cups of salt i need to add to get the SG
i want. It's not that big of a deal if i'm off a little bit either. The main thing is to get it at or above 1.0125 which is what my main tank sits at. I will, however, be purchasing a refractometer soon...which is a more accurate way to test SG
. They go for about 40-50 bucks.
When i do a PWC
, i syphone out the old water. Then to get the new water in, i basically start dumping the new water into my sump and turn the main return pump on as i'm doing this so that the new water is pumped up into the main display tank. This is another benefit of having the sump. You can just dump the water in there cause the sump sits just off the floor. Some folks use a pump to get the water into their display tank. Others just bucket it in there. You can do it however you want.
You can use pool sand, but make sure it's not silica based. Silica based sand can release unwanted particles into your system that can harm your fish. It's recommened to get a aragonite based sand for SW
tanks. Usually, a finer sand is good as well. CC
can trap unwanted nitrates and then release them back into the system with the substrate is disturbed. So if you do go with CC
, you then have to vaccum the CC
regularly to pick clean it out.