agabr123

Hello from the freshwater side of the forum!

I don't really have the resources for a saltwater tank at the moment although I'd love to start one eventually, but I was looking through pictures and a question popped in my head. In tanks that have lots of live rock, anemone, coral, etc. do you take that into account when stocking? For example if you have a 125 gallon tank with 90 lbs of live rock (I have no idea if that's anywhere near accurate but just bear with me ) that's going to end up putting the actual number of gallons of water your tank can hold at much lower than 125. So would that mean that you have to measure how much water is actually going into the tank? I know the same kind of thing happens in FW tanks with substrate and decorations and such, but my thinking is that it's nowhere near the same scale as pounds of live rock.

Anyways, thanks all for reading my ramblings and entertaining my question!

au01st

Yes, it must be taken into consideration, as well as the loss of swimming room. Because live rock is used as part of the filtration system in a SW tank, you want as much of it as you can get. Higher quality rock is very porous and lower quality cheaper rock is more dense. The more porous the better as that is more room for beneficial bacteria.

In general, you want 1.5-1.75 pounds of live rock per gallon. Depending on what kind of rock you buy, you can figure out the displacement and give yourself a rough estimate

agabr123

thanks! since higher quality rock is more porous wouldn't that also mean that there is technically more water in the tank than lower quality one? (perhaps the amount is negligible though)

au01st

Yes, but the space itself is still taken up by the rock. I was only bringing that up because 100lbs of premium fiji @ 9/lb will be more rock than 100lbs of base rock at $4/lb. More dense rock is heavier for the space and you will need more to fill the same area.

agabr123

oh i understand, so for higher quality rock you have to use less so it leaves more room for the water.

thanks for your help!

Hypnox

For my tanks as an overall I take a look at how much rock I have compared to the swimming room my fish typically need and also try to factor in their waste output. Some fish are far far dirtier in the SW world than others, just like in the FW world. My current project is a 40B with a 10g sump, hope to have pics up soon, that has 6 relatively low waste producing fish in it. Also, with SW tanks you should factor in your inverts on top of your fish, snails poop more than you think.

Just like FW, it is a balancing act to figure out the perfect place between # of creatures and the waste they produce.