Got screwed by a fish lol

How would the fish cause algae problems? Did you add the water from the fish bag to your tank?

yeah,did you pour the water from the bags in to your tank?

Do you have any readings for ammonia/nitrite/nitrate? Any pics of the algae?

Just a theory, but overstocking the tank could have lead to a spike in params, and a concurrent algae bloom. A 10g isn't suitable for a rainbow shark.

The problem is you bought a fish at a store that don't know foul mouth what they are doing. I never ever bought a fish from them and if I did it would be going into a quarantine tank. I'm guilty because I sometime don't quarantine but I know the fish are healthy or not by looking at them.

Overstocked was perhaps the wrong term to use...did you cycle the tank beforehand? If so, how? If there's not enough of a bacteria colony to handle another fish, although they do multiply fairly rapidly, it still make have caused a spike. That's why I asked for specific ammonia, nitrite, and nitrate readings.

And it definitely would have been overstocked shortly down the road. Tiger barbs should be in larger groups and therefore need more space. There are also zero pleco species I would keep in a 10 gal. except smaller species for breeding purposes only.

As a general rule, it is always best to quarantine new fish anyways. Especially if they are from, shall we say, "lower" end chain stores.

Fish can be carrying disease and not show signs of it in the store. That is why you should always quarantine for at least a week before adding to your other tanks. We've all learned this lesson the hard way, but one mistake should be enough to convince you that a quarantine tank is a must have if you decide to add fish. It can even be a rubbermade tub with a seeded filter. Doesnt have to be a special fully set up tank. Just somewhere the fish can hang out while you make certain they're not carrying any disease. Most box stores like walmart and petco/petsmart will have sick fish. And if one fish has it, all the fish do even if they're not showing symptoms. Their filtration system is generally tied all together. That is also why you should never dump fish store water into your established tank. Net the fish out once they've been quarantined and get rid of the water they were kept in.

Occasionally if I buy fish directly from a local breeder I trust, I wont quarantine, but that is the only time I dont set new fish up in their own tank for 2 weeks.

Also, are you sure it is algae and not fungus? Pictures would be helpful. My guess is the algae bloomed after the increase in bioload. Also could have been present in the water from the fish store if you dumped it right into the tank.