Tetras Bothering Gourami?

I have a small school of serpae tetras and I think they may be bothering my opaline gourami! He's been resting near the bottom much more often than usual (given I've had him for a week or so) and he seems to chase the tetras away whenever they come close! He also got very dark the other day when nothing seemed to be wrong (I check the water and it was fine) can anyone tell me if he's distressed by the tetras or if it's possible they may be bothering him in some way?

 

Few questions-
1. Tank size
2. Temp
3. How many of each fish and what other fish do you have
4. How was he acclimated
5. Could you give a tank shot? This could help on determining with there aren’t enough places to hide that could cause him stress

 

1. 20 gallon long
2. 76-77 degrees F
3. 4 tetras, 1 gourami, 1 2" bristlenose pleco (originally he was with 5 tiger barbs but I had to get rid of them because there was one barb killing the others, but they never bothered him.)
4. Unfortunately I only floated him, although he didn't have any negative reactions, like I said he's been there for a week. For the tetras I floated/mixed tank water into their bag so they got better acclimated.
5. I'm not sure what a tank shot is, but there are plenty of places to hide

 

I think "tank shot" means post a photo (shot) of your tank.

 

Maybe! I'll have to wait for a response, thank for your input!

 

A tank shot is basically a pic like this-
fish tank
The problem may be caused because the tetras don't have enough of their school, Serpeas are a little different than some tetras In the respect that its recommended for them to have a school of at least 10. the reason being is that they are relatively semI aggressive and if they aren't kept in higher numbers they tend to be mean to other fish(whereas when in the higher numbers the aggression is spread among themselves). Have you noticed any aggression from them?
Also what were the exact parameters/do you use a liquid test kit? Do you have dark substrate?

 

I was unaware of the numbers needed! Ive read that 4 would be okay. I've notice there's one tetra that sometimes swims off on his own but he always returns to the school.
I'm unsure of parameters right off the bat, but I know my alkalinity is a little low (I'm working on fixing that), but I used strips currently.
My substrate is dark blue and white.