The 3x5 Photo Tank will hold larger fish than the Micro Photo Tank, and will also hold several micros at once, allowing easier comparisons to aid identification.
The 3x5 Photo Tank is almost 3.5" deep and almost 5.5" long (inside measurements). It is about 3" front to back (which for for anything other than a water tank would be called depth). Small sunfish, which do not fit in the Micro Photo Tank, and which are notoriously difficult to identify, fit in the 3x5 Photo Tank easily.
The bluegill in the tank is large enough to positively identify without a problem, but having the tank still makes it easier to get a good photo and allows the fish to breath while you are doing it.
Having a photo tank that is large enough to hold several micros at once makes it much easier to compare similar looking fish. Many micros share the general color pattern of olive/brown back, white belly and a black stripe down the side. Subtle differences, like eye size or the width of the black stripe stand out when the fish are side by side.
Micros seem to settle down a bit better in the larger tank, particularly if there is more than one fish in the tank. It is thus easier to get a good photo, which definitely aids in identification.
The tank is not so large that it is cumbersome to carry, though. The tank's corners are all rounded and it is molded from a single piece of plexiglass so you do not have to worry about leaking joints. The lid is hinged and can be closed to prevent fish from jumping out.
The 3x5 Photo Tank is large enough that you can lower a still-hooked fish directly into the tank immediately after it is caught, so the time it is out of the water and gasping for oxygen is minimized. Also, the tank is large enough to dip your hand in so you never have to handle a micro with dry hands. It is large enough that you can use the Dr. Slick Spring Creek Clamps (very highly recommended) to unhook the fish while it is in or directly over the tank so if it slips out of your hand it slips into the water. Finally, since the tank will hold several fish, you can finish fishing a pool and then go to the water's edge and gently pour all the fish into the stream or pond at once rather than throwing them in from the bank.
Studies clearly show that fish handling practices have a major impact on post release mortality for trout. I doubt that anyone has studied post release mortality for micros, but I have to believe that good fish handling practices will maximize the number that will survive to be caught again and to make more baby micros. Please handle with care.
To see the 3x5 photo tank in action, take a look at Leo Sheng's Extreme Philly Fishing YouTube episode where uses his for the first time: https://www.youtube.com/watch?v=NSDdD9Q9WvQ
Domestic shipping is $10 via USPS Priority Mail (2-3 day delivery).
The charge for international shipping depends on the destination country, the weight of the package, the overall length of the package and the value of the package. Packages under 24" long and under $400 in value will go via USPS First Class International. Packages over 24" or over $400 will go via USPS Priority Mail International.