Sorry to be the bearer of bad news but Platies and hill stream loaches are not compatible.
http://www.seriouslyfish.com/species/sewellia-lineolata/
That flow rate is too strong for Platies.
Ya i have been considering moving them over to a different tank.
The way my current setup is the flow is much greater at the top and back of the tank. The platies seem to actually enjoy swimming between plants when relaxing and swimming through the current when i feed etc. There is a large piece of former dry reef rock which interrupts flow pattern a lot. Along the back wall the flow is strong and, although i do not achieve a completely unidirectional flow throughout the tank, the back wall seems to simulate fast streams enough for my hillstream.
I was conscious of this difference prior to the platy addition (i kept a single platy in a ten gallon and moved him over to see if it would work). I used to have one but have since increased to four (3 females). I run the tank without a heater and a powerhead that is rated at 528 gph (in a 20). But i have kept salt for a long time and i am fairly certain flow rate is closer to the 250 ish range. I have an airstone for added aeration.
Anyway the tank is a year old and i have kept the two fish together successfully. (Just to emphasize, i have heard quite a bit about hillstreams dying stuck to the glass, etc. He is a year old, i assume i would have noticed negative impacts by now) [he has grown a little and no weight loss]
My older platy has been fine for the year. The three new fish were added last month.
I have been debating just making my scud tank a platy tank and if i notice any issues with the platies i will not hesitate to move them.
But anyway, do platies actually eat scuds? (Regardless of what i end up doing with the platies this will be useful info)