Building custom tank

The deeper the tank, the stronger the lighting you will need, but lighting will also depend on what you keep for corals. Consider this too......... The deeper the tank, the harder it is to reach the bottom.

Swull
Also you have to remember, if you get a deep aquarium, and you have some light dependent sps's you can always arange them higher up in the aquarium display and still enjoy the larger viewing space of the taller tank.

At 24", Using multiple combinations of 175w, 250w should prove successful.


Regards,
Twize
My Tank Specs
www.Twize.com

I would go with the 20. While the increased depth of the 24 increases the volume and swimming area, it will not increase the surface area, and surface area is more restrictive than volume in terms of stocking.

I guess we need to see the big picture of your total projected setup, the surface area on a tank this size is no issue if you have the adequate equipment setup (sump, refugium, skimmer, water flow amount etc...)

IMO and from my experience on my Big tanks and reef collegues (also with very large tanks), 4" is not much of a concern for lighting @ 20" . Believe me many of my colleagues grow light needy sps's in +30" tanks with 175w MH. Again, its what your willing to spend and If you have the means to purchase the bigger tank along with the (key) "appropriate equipment", you won't be unhappy with the results.

Thx,
Twize
www.Twize.com