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1 ID Shark
2 Tin Foil Barbs
3 Mollies
2 Rosy Barbs
2 comet gold fish
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I know the ID sharks and Tin foils will outgrow my tank, will upgrade when they gain size.
** I want to know if tigers barbs (5) will do fine with others and if they will overcrowd the tank. **

I have efficient filtration and do regular water changes, so water quality is always uncompromising.

Unless you plan on upgrading to a lake, you might as well find a new home for the ID shark now. Goldfish are cold water and dont really belong in that tank, the comets also get far too large. So no you can't have tiger barbs.

The ID shark and tinfoil barbs may be going into a pond when they over grow the tank, but being in a tank that is far too small, such as that, is extremely stressful. Even for the comet goldfish.

pets question and answers,www.5d2d.com

When you say 1 ID shark, 2 tinfoil barbs and 2 comet goldfish, you don't say how big they are, but even if they're about 2 inches per fish, with the tiger barbs, it could be overstocked.
Also, when you say you do regular water changes and have efficient filtration, all of that is a matter of opinion. Most people would say that a filter for 10-20 gallons would be efficient on a 20 gallon tank, but I'd never put anything less than a 40 gallon capacity on a 20 gallon tank. And some people think that a 10% water change monthly is efficient, while others like myself prefer to do at least a 10% water change weekly. Everything is subjective but keep in mind that goldfish typically are dirty fish who produce a lot of ammonia.
All in all, I wouldn't do it, but should you do it, they would likely be fine as long as they aren't overly aggressive like the few I've been stuck with have been. I would much rather house the comets, shark and tinfoils in something like a 55 gallon tank.

aqadvisor.com, and about 6 years of freshwater fish keeping experience.