People will say 'anything' to put you off if they can because they think their opinion is right, Its easier
to say something along the lines of 'a small tank wont cycle' to put you off using a small nano tank rather then explain that with small tanks you have less space to fill with nitrates/bio-load which have to be reduced by water changes, a small tank may need a water change every other day compared to weekly or fortnightly with larger tanks. The Bio-load of a fish is HUGE compared to a few Opae ula shrimp and the quantity of waste the shrimp produce that gets turned into nitrates will be enough to feed the algae in your tank thus being reduced without the need of water changes!
Your tank is two gallon? i have a 17 gallon tank with about 300 Opae ula in it and my nitrates are a constant zero, it works out about 17 shrimp per gallon, if you have 10 - 15 in two gallons your water will be healthier then mine so long as its cycled.