Hi Ann,
I hope the Melafix sorts the RC, remember to change change out 25% of the water after treating it daily after 7 days.
The GT will if you leave him will treat the tank as his and make it difficult to add others if you leave it too long. the good news is - you must add more fish -
I don't know all the dimensions of his tank so I calculated it as 48" x 12" x 16" :
System type Tropical freshwater aquarium
Dimensions 122 x 30 x 41cm/48" x 12" x 16
Surface area 0.37 sqm/3.98 sq ft/ inches sq in
Volume 151 l./33 gal. (39.89 US gal.)
Probable volume 136 l./30 gal. (36 US gal.)
Stocking density
30"/76cm (built up gradually)
The shrimps and the frogs will be fine in the BiOrb, you could probably 'clutter it up' a bit. If the BiOrb has a built in light something like
THIS is cool, though the same can be achieved with placky/silk plants to much the same effect, but do not offer the microscopic beaties that live and breed on plants (which the shrimps constantly graze). The frogs being quite short-sighted and slow rely on their sense of smell to hunt and because the BiOrbs flows/currents and shape has changed, it will take the time to realise when the food will be & when. Because the floor surface area on BiOrbs is very small in relation to the water volume, and because you are keeping 2 kinds of animals that use walking/crawling as there main living area, the larger the area they have to explore the better. You can do this by piling a lot of 'things' to walk all over or rest on, out of each others way.
You don't say how large the Goldfish tank is, But I'd tend to keep the tropical stuff in the largest tank, basically it means I can keep more fish in it.
I have a 30 gallon bendy plastic store-it box from B&Q (£10) with a small power filter and a heater stuck to the side of it. I has 14 Cardinals and an Elephantnose fish in it in quarrantine . The melting point of Acrylic is about 130c - so as long as you keep it suckered to the side and don't let the actual heater glass touch the sides or bottom it will be fine - if you can, Aim or place the filter or bubbler at or close to the heater to dissipate the heat.
Dwarf Gouramis are nice and fairly placid and being slender, deep bodied fishes, the look better and more colourful that say, danios and such that make much less of a visual impact. More 'bangs for your buck' - kinda.

I would get 3 or 4 to make sure you get a male at least, because he's the one that will have all the colours and a female to display to. See
This btw :
One drawback to this species is that it seems particularly prone to bacterial infection and Nocardia or Fish TB-like disorders. It would be highly advisable to ensure that any fish you purchase are plump, colourful and feeding well, and completely free of sores or red marks before purchase. Treating the bacterial infections these fish tend to carry is often unsuccessful. Some shops no longer stock this species as some suppliers in the Far East seem unable to provide disease-resistant fish. If you're able to find decent stock, they should be very easy to keep once you have them established in your aquarium. [Ed's note: Recent research, published in 2006, has shown that up to 22% of Dwarf gouramies exported from Singapore carry an Dwarf gourami Iridovirus (DGIV). This harmful disease is likely to be the cause of losses.
A good idea to add some small fish to the shrimp tank, as most of the frogs/shrimps ill be on the floor or ornaments and it will look nicer with the the rest of the tank utilised.
Neons,
Cardinals,
Emperors,
Endler's,
Harlequins,
Galaxi's etc.
I plan to have a school of Cardinals in my shrimp tank.
As for the RC's tank - I would have some dwarf Cichlids with him (far more personality and are interesting) like :
Double/triple reds peacocks,
Borellii's,
Agassizii's,
Hongsloi's,
Panda's....
As for the your big tank, if you like Silver Sharks, I'd get another 4, as they are much happier in a school and you will see the difference in your little chappie.

If you don't have any live plants,
Silver Dollars are nice showy fish that don't get too big and are fine in a four footer.
Just remember to re-arrange the deco in the tank when introducing any new fish, so they all have to sort out new territories and are all on equal footing together.
Have to go now, as all this typing has given me RSI.
Let me know how it goes....