missing fish

Question
QUESTION: Thanks for helping.  I don't understand something.  I have "lost", literally, one pleco, one guppy (the other 3 died) and one cory.  They just disappeared.  My tank is new, started on 10/19/10 and appears to be cycled.  I found one Platy dead this morning.  All levels are normal.  I did treat for brown algae on 12/17/10, per my LFS, but I only treated once and bought the plecos (2) that day.  I will not treat for algae again as I read it wasn't necessary.  I have a 20 long which I test every day.  What do you think is going on?  Is this normal?  Thanks again.  Let me know if I haven't given enough info.  I'm new at this.

ANSWER: Tricia,
 
 You have found out the hard way that most people at your LFS do not know anything about fish and things that need to be done for them. Not sure how a tank can "appear" to be cycled. The only way you can know for sure is testing the water starting 2 weeks after you have set it up. Its very hard to have one fish vanish let alone 3. I am sure they are in there the bodies that is or they have been eaten. I am still thinking that if you have purchased all the fish from the same store they might be having a problem. If I buy fish from a store and they start dying I don't buy from them any more. It could be the breeder they are using. I am not understanding how all the levels can be good. What are the water readings?

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

QUESTION: Thanks, Jaymie, for responding quickly.  As far as the levels are concerned, I have no ammonia, nitrates at .10 and nitrites at 0.  I have ordered a kit for checking phosphates as my research suggests that could be part of the problem with the brown algae. (?)  I know it's not correct, but I did a 40% water change last night to clean up the rest of the algae and look for bodies, but I didn't find my little guys.  Tank is clean though.  And, I was told (again by the LFS) that my tank had cycled if these readings were low or non-existent and I had brown algae.  Thanks again for the rapid response and the concern you showed.

Answer
Tricia,

 Not sure why they would say your tank is cycled if you have brown algae. None of my tanks have algae except my fry tanks. They tend to get get algae since the tank light is on longer. As long as the cycle took 3 weeks with no fish then I would have to say the tank did cycle. Hopefully you will start to have better luck with your tank.