Live Rock for 230 Gallon Tank

Hugh Mann · Feb 2, 2021

I have read numerous times the "Rule of Thumb" when it comes to live rock is 1-1.5 pounds per gallon.

Does that scale with large tanks? By which I mean would it be recommended to buy 345 pounds of rock?
Does that include the volume of the sump, which is 150 gallons, so probably 75 gallons of actual water for another 112lbs of rock?
Or is there a point where a certain amount of rock is just enough?

Trying to sort out how much rock I need to source when building this beast up. Also, while I know it is recommended to start with cured live rock, depending on how much I need, it's just not possible for me to afford it all, and will have to use some dry rock as well. Is there a recommended ratio of live and dry?

If it matters, my planned livestock is a mix of cave dwellers/perchers and open swimmers, though I haven't settled on a definite list.

brandon429 · Feb 2, 2021

This is an easy test for surface area mechanics, the rule of thumb has no application and by that I mean some of the top reefs currently running Rev has used as focus examples in posts use a tenth of the stated rule and still run a full fish load. If you buy thirty pounds of live rock and put it in the tank, that will carry the full fish loading the tank will ever see, more isn’t needed, we’ve all been trained to overdo surface area grossly (and now bommie aquascapes undo that rule, keep as many fish)

all dry rock you add will become cycled in twenty days by being in water with cured live rock. All you need is a crate of pre cured live rock, add it, and you just skip cycled. The extra two hundred pounds of dry will present curing challenges but the cycle will have been skipped for the system in the common sense, where goes live rock goes a skip cycle, adding a bunch of inert material doesn’t make the live rock weaker.

in summary: thirty pounds of live rock and X pounds of dry rock will carry the same fish bioload that four hundred pounds of cured live rock will carry. I know that seems backwards from the truth, but it’s just because all the rules we use for framing out a reef tank have been made up. Bommie reefs with thirty fish will die quickly when this becomes untrue.

*there is a bioload maximum carry differential between thirty pounds and four hundred pounds of live rock-the trick is that in a home reef aquarium we cant stack so many fish as to overcome the thirty pound approach. It’s not like adding hundreds of pounds of live rock will carry 400 fish, the box isn’t big enough. For all the fish and bioload you will ever see in that big tank, the surface area from 30 pounds is enough. Once the dry rock portion catches up, we are back to being entirely overdone on surface area and waste catchpoints like a typical reef tank.

Hugh Mann · Feb 2, 2021

That is extremely informative, and is very useful to know, thank you very much. This information should be a sticky with big, bold, friendly letters.

Yup, definitely useful. The challenges posed by using mostly dry are definitely worth it saving enough money to buy half my fish.

Thanks again.