Aquarium Plants

Question
QUESTION: Hi, I have a 11.8 gallon aquarium with 4 gold fishes. I kept alot of water plants as suggested to give hidding space and convert CO2 to O2 and nitrates and nitrites etc. The plants dont seem to be doing fine and I am worried that they all will die very soon. One site suggested to put some yeast in the water as its an anarobic bacteria converting O2 to CO2 which can be good plants too. Please advise, if I can do so to save the plants and what should be the measurement for the Yeast powder.
ANSWER: You should never add yeast directly to your water.  I would guess (without seeing your plants or your tank) is that your water quality is off.  11.8g's is too small for one goldfish, let alone 4.  Plants are sensitive to high levels of ammonia, nitrites and nitrates the same as fish.  I would look into this before trying to add CO2 with yeast.

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QUESTION: The size of the aquarium is length 3feet, hieght 1.25 feet and width 1 feet. This is a standard size available here in India. The water quality is very good and I have only fish and natural plants giving alot of movement space. I understand that its too small for GOld fish but there size is only 2 inches at present. The leaves are wilting may be becoz of lack of CO2 or other neutrients. There is nothing available here called fertilizer for the plants in India and I am keen on saving all of them. Please advise how should I put CO2 in my Tank to save them
ANSWER: Here's a site on how to make your own CO2 injector for your tank.
http://lehtis.arkku.net/enghiilidioksiidinlannoitin.php

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QUESTION: Hi, one of fish always stays in natural plants and comes out only when food is given. It stays at the bottom and almost does not move. There is no sign of any disease and it eats just fine along with others. Please advise.

Answer
He could just be at the bottom of the aggression pecking order and is choosing to stay out of the way.  Fish seem to put their differences aside when there is food.  I have a female danio that spends most of her time on her own and that is just what is normal for her.  If the fish is not suffering from stress or disease and is still eating, I wouldn't worry.