Water volume and chemistry

[steve888]

Debating to setup 90G or 40G SPS/LPs tank. Does a 90 gallon tank holds more Calcium, alkalinity and Magnesium than 40G due to water volume? In other words it would take twice as long for the SPS/LPS corals would have consume Calcium, alkalinity and Magnesium on the 90 gallon compared to 40 gallon?

If I can get away without having to perform two part dosing on the 90 gallon and just perform weekly or bimonthly 20% water changes.

[Mariaface]

If you have the same amount of corals in either tank, the 90 will have more cal/alk/mag available, yes. However, those corals are going to grow in and begin to consume more. If you have the same proportion of corals, it'll take the same amount of time. This is assuming lighting and nutrients (and feedings) are all the same.

[steve888]

Thanks, so the 90 would require more dosing compare to the 40 due to its larger volume? In long run the 90 would require more resource to run? I am growing only sps and acan frags in either 40 or 90 gallon.

[Mariaface]

If you took the corals out of the 40 and put them in the 90, you'd be dosing the same amount as you were in the 40. Dosing amount depends on coral growth, not the water (the corals are the ones using up alk/cal/mag). Once the corals grow larger or multiply in the 90, dosing goes up to keep up with coral mass and growth. However, dosing would've gone up in the 40 as well if the corals continued to grow.

 

In the long run, the 90 will require more resources in terms of lighting, water changes, etc, but that's because you'll need to light a larger area, change out more water to get the same percentage, replace stronger equipment, blah blah blah. The up side is that you can fit twice as much in the 90.

[steve888]

Thanks much I got it now.

[Themerchant]

good advice