fish and what kind to get

Question
QUESTION: We have a 20 gall tank , at our local  library and recently , some algae has gotten into it, and ended up killing all the fish , which were small . then yesterday we got a pleco and two goldfish  and thought they were doing well but come to find out , today when i get here that both goldfish where dead ! what kind of fish would thrive in a 20gall tank ?

ANSWER: Hi Jennifer,
Algae does not kill fish, it just looks unsightly and people do not want it.  However some algae do show if the water chemistry is unbalances such as high nitrates.  It must have been water quality or some other reason.  If both goldfish died the same time, its the water.  Did you put conditioner/dechorinizer into the water before adding fish?  Plain and untreated tap water contains chlorine which is toxic to fish.  Your fish will do fine in a 20 gallon.  If the chlorine is not the reason of your fish's death, reply back and give me the following info.
How long as the tank been set up?
What are the ammonia nitrite and nitrate readings?
How often do you feed?
Do you do any water changes?
How are they acting before they died?
-Matt-

---------- FOLLOW-UP ----------

QUESTION: what kind of fish would be best for my 20 gall tank ?

Answer
Hi agian Jennifer,
Any live-bearing fish such as Mollies, Platies, Guppies, Swordtails, and Endlers.  Or any fish that stay small and do not get big.  Goldfish all get big and have a big biolad so I would recommend a bigger tank for goldfish.  Common plecos get 12-14 inches and I do not recommend them either unless you want to keep them for a short period and give it away further down the road.  Other plecos such as bristlenose plecos stay small and thouse would be good.
-Matt-