Best way to transfer fish to bigger aquarium?

The same way you put them in the 10 gallon. Get a large fish-bag, similar to the ones you brought them home in. They should still be small enough to fit. Fill the bags with water from the ten gallon and add the fish. Let them adjust to the temperature in the new tank for half an hour at least. Every ten minutes, add some water from the 55 to the bags.

You have two options here - you can fishlessly cycle the 55 gallon for roughly 6 weeks using pure ammonia and some filter media/gravel from the 10 gallon, or you can put the fish into the 55 and cycle it with the fish. Use all the gravel and filter media from the ten gallon to help transfer beneficial bacteria and do daily 10-25% water changes until the cycle is complete.

Normally I am a massive advocate of a fishless cycle, but for these heavy waste producers, I'd do the fish-in cycle. Their waste will be more diluted in a 55 gallon, and it's better than a 10, especially if the 10 is still cycling.

Please be aware that whilst the 55 gallon is perfect for a fantail or even 2 or 3, a common pleco will probably outgrow it. Most 55 gallon tanks are only a foot from front to back. A common pleco will grow to 18 inches and be unable to turn around. They need 75 gallon tanks. Furthermore, although they can adjust to life at cooler temperatures, plecos are tropical fish and will have depressed immune systems in cold water, being more prone to illness and finding it harder to recover. They really shouldn't be kept below 73F, which is too warm for goldies to be happy.

Drain Half the water from the 10 gl tank and refill from the new 55 gl tank.

The next day do it again. ---With the fish in it each time.

The next day put all the water and gravel and rocks fish etc... in the 55 gl tank

I would also recommend that you get 2 more Pleckos and 3-4 Chinese Algae Eaters and 4-6 Gravel Eels and 5-8 Ghost Shrimp. You will need these just to keep the tank clean. Fill the rest with whatever you like. The rule is 1 inch of fish per 1 gl of water which is 55 inches of fish TOTAL.

The Pleckos will get up to 10 inches each but remove 1 after the other 2 are 5 inches each, so thats say 16 inches total after awhile

The CAs will get 3 inches each thats say 10 inches there

The 5 Eels equal 2 fish 3 inches long so thats 6 inches

6 GS will equal three 1 inch fish so thats 3 inches there

total so far is 35 so you can add up to 20 more INCHES of fish of any community fish of your choice

This will help ensure a well balanced tank.

You didnt say what kind of filter you are using but Id recommend a WHISPER Brand.

The use of LIVE plants can introduce SNAILS (the little evil ones) BE CAREFULL here.

Provide ALOT of hiding holes for the fish

Ideal Temp of 78 degrees.

GOOD LUCK to YOU