I’d suggest starting by working out a temporary livestock holding tank, such as a plastic stock tank! — such a thing can even be drilled to drain into your existing sump!
It’s been my experience that no 50+ gallon tank upgrade happens end to end in one day… at least not when things are being done even remotely correctly! Usually, it seems to take a week or two to really get the new tank set up and stable after all the rearranging! (For example, one defective part? Too bad. You’re stuck waiting for a new one to ship in many cases!)
Once you have your livestock and rock in a solid holding system, you can proceed to take your time breaking down the old system, and installing the new one! (getting the stand leveled out, getting the tank and sump installed, Plumbing everything, wiring, leak checking, etc…)
— the old Red Sea tank may be easiest to get out without help if you simply cut it apart to glass panes with a razor blade, moving the panes out one by one! Then, you can donate them to a glass cutter, or save them for future projects!
Regarding plumbing, there are numerous ways to go about it, but do know that you will need to cement some pipe into some fittings to get custom plumbing fitting and looking nice!
Here’s a recent discussion on the subject to hit some points I’ll likely miss here (post #155, #167, etc…):
https://www.reef2reef.com/threads/box-of-crayons.1114489/page-8
— I recommend using bulkheads which have threads on the nut side of their body, this allows you to actually disassemble the plumbing down the road to replace the rubber water seal “gasket” on your bulkheads without cutting any plumbing! (If you cement a pipe/fitting into a bulkhead, you have to cut said fitting off to remove the bulkhead from the hole in the tank glass!)
— design your drains first, they perform best with minimum amounts of pipe parallel to the ground, and should never gain elevation during each pipe’s path… the return plumbing can go in after the drains; it’s pressurized, thus less important to make a straight shot with!
— you will likely want more elbow fittings on hand than you think you need (both 45* and 90* elbows), just so you can get a bit creative with where pipes end up going! Also, unions are your friend! Anywhere where you’d have to cut the plumbing to take it apart, a union creates a quick-disconnect! (Unions are also great against bulkhead fittings, allowing you to decouple plumbing from tank, and helping to keep the bulkheads from loosening/starting to leak if the plumbing gets yanked on!)
— you will not be able to easily bottom-out a pipe all the way to the shoulder inside a “slip” (aka “socket”) style fitting unless cement is used, or the fitting is physically oversized, thus defective….
Because you cannot reasonably get the pipes and fittings all pressed fully together prior to final cementing, I find that using slightly undersized pipe lengths works well to mock things up, getting the pipe going exactly where you want with pipes just friction fit into fittings…
This allows you to measure the length of each pipe, from fitting lip to fitting lip. That is the target amount of final pipe between two fittings… you simply measure/add each fitting’s socket depth (measured from socket lip to socket shoulder) to the total pipe length… this is your final cemented target pipe length!
— I tend to go one cemented joint at a time, working my way along a pipe run getting each joint together while periodically test fitting to make sure I haven’t made an errors anywhere… I don’t recommend trying to do multiple cemented joints simultaneously unless you absolutely have to, as this is a good way to make a mess and need to redo a pipe!
I’m definitely forgetting several things here, but that should be enough to help you start wrapping your head around the concepts!
— Don’t be afraid to ask if you have any general, or specific questions, either!
