Tank size and shape...FYI

[Sk8r]

I offer this for those of you out shopping for holiday tanks.
A tank is an investment---and it's even more so when loaded. So it's important to have an idea where you're going---what aspect of the hobby most inspires you, (and sadly, what can you afford?)---and is this to be THE tank or only A tank to get you started. If you're going to surprise someone with a tank---best really to get a gift certificate and let that be the surprise, because a tank's characteristics do set what it can be used for.

So here are some things to think about:
reef-ready, drilled, or not-drilled or all-in-one.
A reef-ready tank comes pre-drilled for the piping and has a "downflow box" which otherwise you would have to buy. It is generally overflow-proof, or as much so as you can hope. Basically, with a reef-ready tank, you are set up to connect to a Sump (another tank below) that will contain all the less decorative equipment (skimmer, heater, GFO reactor, return pump) that needs to fit into your stand.
A non-drilled tank still needs to have thick enough glass to protect you from cracks and bottom splits (rock can be heavy, and we have a lot of it!) And if you intend to drill it yourself, be sure what panes are tempered and what aren't, because drilling tempered glass will shatter it to tiny bits.
An all-in-one is a little tank, 30 gallon or less, that is what it says. It has enough equipment miniaturized to support a few basic corals, inverts and some fish that have an adult size no greater than 2-3".

Acrylic vs glass:
Acrylic is light and far less spendy, but cleaning coralline off the walls is a pita. It scratches almost as easily as an acrylic water glass, and most cleaners will scratch it. It goesn't often break, but has top braces to keep it from bowing to the point of breaking or popping a seam, and those may get in the way of light.
Glass weighs like sin (my empty 54 g weighs 84 pounds bone dry) but you can use a razor blade to clean it. It will break catastrophically if hit.

shape:
Tanks come in "tall", "long", "corner bow", "corner," "cube", "hex", and a few more exotic. In general, better a bend than a seam. Seams are weak spots. Problems waiting to happen. Curved glass costs more. And---a detail many don't imagine---a corner tank doesn't have a very big stand---so you save on the stand---but you have NO room under the stand to put a big sump! So if you want a refugium---you have to do a display fuge, or drill your floor to put a sump in your basement!

Shape matters bigtime when you're considering the expense of light kits---and when you're considering what fish you want. If you want the larger reef fish you definitely need 'long', you need "tall enough" and you need gallonage to boot...75 gallons and over...because most need the long run unimpeded by rocks. Habit and size requirements of the particular species will vary even within a 'type' of fish.
If you want stony coral, 'tall' gives you an array of distances from the light, and 'cube' or 'corner' gives you more coverage of a single light, versus lights strung out down the length of a fixture. A long tank for stony coral means you spend more in lighting.

Gallonage:
Tanks start at 3 gallons, and go upward to the Atlanta Aquarium.

Corals can live in any sort of tank as long as their calcium needs and lighting needs are met. Even a 3-gallon can be a reef. Do corals grow to fill bare space? Ask my bigger-than-a-basketball hammer coral. It started at 2" with 3 heads. I haven't counted them lately.

Gallonage for fish goes upward, of course, and generally long shape and the highest possible gallonage are good bets if you want to keep an array of fish and if you want to keep the larger reef fishes. If you have limited length, the blennies and gobies and other fishes that keep close little territories and don't stray far from 'home' are a good bet. Along with length, of course, gallonage tends to increase, and with it, the fish variety becomes greater...but your lighting costs go up.