Flying with a fish domestically is allowed by TSA. It may not be allowed by the airline carrier. But as long as you keep it in your carryon they don't have to know about it.
It is different for bringing in a fish internationally. That is technically importing a species into the U.S. and...
OK you don't have barbs. What you have there are two Von Rio tetras (Hyphessobrycon flammeus).
Although a larger tank is always preferable, I do not believe that it is necessary for 2 of these guys. Many breeders actually breed their tetras in smaller (2.5 gallon) aquariums.
Corydoras...
Your tank is too small for all those large Malawi Haps. You might be ok if the fish are all immature juveniles for awhile. But as they grow and mature there is going to be a bloodbath.
A 150 would be a better choice for that group.
The proteins bind to the surface tension on the bubbles (like the skin on soup). The bubbles then push up and into a collection cup, essentially removing this organic material from the water.
Proteins contain nitrogen, phosphorous, and extra carbon which would eventually break down into...
The first one is a Melanochromis exasperatus. (a species of Malawi mbuna). The second one is a Zebra obliquidens (Astatotilapia latifasciata), a Victorian hap.
Andy
I was thinking jailbirds (Leporinus fasciatus). but they get too big for a 20 gallon tank.
The decorations are all hand painted. Assuming they fit safety standards for children's toys they should be safe for the aquarium. However the paint will likely flake off over time.
Elegant corys are a small species and 5 in a 10 gallon should be no problem. Bigger is always better, but many cory breeders (including myself) use 5-10 gallon aquariums for small breeding groups of smaller species.
Andy
A 180 gallon is a stock Aqueon size. You can probably find one at any local pet store or they should be able to order it for you. Petco and Petsmart do not carry that size so you are probably out of luck there.
Actual S. petricola are very rare in the hobby. Most in the hobby are "Dwarf Petricola" i.e. S. lucipinnis.
They are perfectly fine in a 10 gallon. That's the size tank I used to use to spawn them in. You can keep a group of 3-6 of them in a 10 gallon no problem.
Just be sure to provide...
It could also be glass corrosion. This occurs when sodium ions migrate out of the glass matrice and dissolve into the water. The resulting skeleton is cloudy. There is nothing you can do about this once it occurs.
The bottom frame is holding up the bottom glass so it is providing support.
Depending on where the crack is I would lean toward it's not anything to worry about though.
A 1" bulkhead requires a 1.75" diameter hole. This should be the size hole saw bit you need.
You are better off buying a bulkhead than trying to make one out of pvc. pvc does not have the flange that the gasket needs to seal against to prevent leaks.
Also Lowes does not sell glass drill...
I was feeding krill, ghost shrimp, and prepared frozen formulas. I never had much luck getting them to feed though. I gave up trying to keep the sharks but may try again someday when I have more tank space.
What do you feed the newborn swell sharks? I have always had difficulty getting newborn coral catsharks to feed properly. Just curious what you do to get them to feed?