Five days is no where near long enough to cause them to switch. Keep at it.
+1
Most people give up too soon, a stubborn fish can sometimes take several weeks, even months to fully convert from one type of food to another, especially when converting from flakes to pellets. I have trained scores of different species of fish to eat NLS, including many wild caught fish, and loaches are by far one of the easiest fish to train.
Remove all other options & in time most fish will learn to love what is offered, no matter the brand. Good luck, NLS is a high quality food & half the price of massivore.