Plecos keep dying after only a couple days other fish perfectly fine

[Calijroc75]

Ok so I have a 40 gallon fish tank fresh water I just added 2 angel fish and a plecostomus 2 and a half weeks ago This past Sunday I had to replace the Pleco because he died it is now the 2nd one that I have replaced him with is also on the verge of death and I don't know why The tank has been up and running to establish itself for a good 3 to 4 weeks before I put the fish in there the angel fish are perfectly fine swimming about just happily as anybody else could be but the 2nd Pleco has died within 3 days after buying it just like the 1st one I know my tank is not overcrowded they are the only 3 in the tank it is a 40 gallon tank and they are babies I have had several fish tanks in the past and have never had a problem like this before He's just a general basic pleco nothing special But I can't seem to keep them alive after 2 or 3 days of having them they diey

 

[connorlindeman]

Ok so I have a 40 gallon fish tank fresh water I just added 2 angel fish and a plecostomus 2 and a half weeks ago This past Sunday I had to replace the Pleco because he died it is now the 2nd one that I have replaced him with is also on the verge of death and I don't know why The tank has been up and running to establish itself for a good 3 to 4 weeks before I put the fish in there the angel fish are perfectly fine swimming about just happily as anybody else could be but the 2nd Pleco has died within 3 days after buying it just like the 1st one I know my tank is not overcrowded they are the only 3 in the tank it is a 40 gallon tank and they are babies I have had several fish tanks in the past and have never had a problem like this before He's just a general basic pleco nothing special But I can't seem to keep them alive after 2 or 3 days of having them they diey

hmmm. Could you please post your water parameters? (ph, gh, kh)

 

[Byron]

Yes, we need the parameters (GH, pH especially), also the temperature. And water conditions if you can test them, this refers to ammonia, nitrite and nitrate.

Second, can you pin down the name of the "pleco," there are dozens of species and they have varying needs.