Trace of marine salt okay for polys?

[knifegill]

I did some digging but don't see any threads addressing the polypterids' tolerance for salt. I just noticed that every species in my 75gal is actually light brackish except for the two polys. I'm not thinking of much, just enough marine salt to bump it to 1.001 or so. So is this a big no-no or has anyone done well with this?

 

[machine]

i've used marine salt wit mine b4 no probs i did a table spoon 4 every 5gals of water but now i jus use API aquarium salt