Why are all the fish swimming on bottom?

Question
I have a 20 gallon tank, with fish in good health.  I added some fish this morning and now there are some funny things happening.  First, here's what I already had in the tank:
1 Rainbow Shark Epalzeorhynchos frenatum
1 Gold/Chinese Algae Eater Gyrinocheilus aymonieri
6 GloFish
3 Neon tetras Paracheirodon innesi
3 Glowlight tetras Hemigrammus erythrozonus  
1 female Flame gourami Colisa lalia

All exhibited normal behavior.  (Sidenote: The female Flame gourami was a little puffy around the midsection, but I've noticed that she sometimes gets puffy but will return to normal in a few days.  She's still eating, no pinecone, and still swimming normally.  So as long as she returns to normal within about a week I don't worry about it. )

This morning I purchased:
1 male Flame gourami Colisa lalia
2 Siamese Algae Eater Crossocheilus oblongus

I went through the normal routine of acclimating the fish to the water.  I floated their bags 15 min then added a little of the current water every 5 minutes before the complete transition. I also added Jungle Labs' StartRight with Aloe Vera.  

After adding the new fish, the Siamese algae eaters seem completely at home.  The male Flame gourami seemed a little distressed at first, but I know that gouramis can get a little excitable and as time passes he seems to be stabilizing.

Now the weird thing:  ALL of my fish are swimming in the lower 1/3 of the tank.  Even my gouramis, which are normally right up top. The gouramis will dart up to the top, hover for a second, and then dart back to the bottom.  Several of them are still eating (picking a few flakes of fish food from this mornings feeding off the gravel and the siamese are eating the algae).

What is going on?  Any ideas?

Answer
Lexie,
To start, you have way too many fish in the 20 gallon. They could all be swimming at the bottom because of adding the new fish. They could also be doing it out of stress. How often are you doing your water changes and how much water are you removing? What are your readings for ammonia, nitrites, nitrates, and Ph? As for your fish that gets puffy, it is not normal for a fish to do that all the time. Be careful with the Gold/Chinese Algae Eaters, they will latch on to other fish. They can actually suck holes in other fish. These guys grow to about 6 inches, and a 20 gallon tank is way to small for them. If there is no algae in the tank, you have to make sure you feed them well. If not, they will start going after your other fish. The rainbow shark also gets to be about 6 inches and the minimum size tank for one is 30 gallons, but 50 gallons is better. I think that problem is too many fish, and too small a tank. Let me know what the above mentioned levels are.