Ich Or Sand?

[Awilcox]

I have a 55 gal mostly african tank that has 2 small oscars and 2 small bichirs (one Senegal and one delhezi) the oscars and bichirs are only temporary in this tank until I move and figure out a better situation for them. I have a large grain sand substrate that sticks to the fish on occasion, although, I am worried at the possibility of ich, as I have noticed white spots on the oscars, but only the oscars. All of the other fish don't have a single spot on them, are oscars more susceptible to ich than the Africans? Should I treat the whole tank? I have 2 common plecos in the tank that I want to spare if possible, and I do not have a hospital tank at the moment. Anyone seen anything like this before?

 

[LyraGuppi]

Is the sand white and small? If not, it may be ich.

 

[sawickib]

Some pictures would help greatly if you could provide some.

And just like to say you have some monsters waiting to grow, the oscars will need a 150 gallon for the two of them and the commons will need a 250+ gallon tank so i hope you have a good system in place for them.