Sounds like you're doing great Xabien!
To address your concerns:
I'm not sure what a "para" pleco is. Is it the little spotted one? Or the more like the common one (its given an L number of 075, but whats listed under 075 on www.plantecatfish.com
is a Ancistomus sp, what comes up in a google search for para is a Hypostomus sp; do find out for sure exactly what you have - some plecs will get twice the size of the clown loaches!). Most plecs are nocturnal, so no surprise he hangs out in the cave most of the time. Plecs also aren't usually very social, so I wouldn't worry if he's zipping back to his cave.
You may have a year or 2 before the clown loaches get too big for your tank; up to you whether you want to hang on to em long enough to get attached or not. You might want to look into some smaller loaches to replace them, such as Yoyo loaches which get to be about half the size. Go thru www.loaches.com
to get an idea of which loaches might fit better in your tank.
aka Cycling Guru and the Ich Slayer
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Card carrying member of FTAS & GCAS.