Cut shrimp into small pieces and put the pellets inside-be prepared to cut the pellets to make it fit if needed. Over time start to increase the size of the pellets that you put in the shrimp. I started with 1/2 Massivore to full pellet.
If it eats the pieces of shrimp with some pellets in then start to marinate the pellets with the shrimp and toss it all in together. I used to leave some shrimp to thaw with the pellets mixed in and then toss it all in together. I then found that the tiger would eight pellets separately at each feeding whilst also eating the prawn. I then just put the pellets in and found they took to this.
I successfully converted an NGT which only ate blood worms when I first got it. I converted it from blood worms to prawn to Massivore but it took about four months and a lot of patience. Under no circumstances starve for long periods of time. Only a few days at a time if necessary. I was told when I was new to Tigers that you could starve them and they would never die-I lost a really nice NGT from this and will never do it again. I've also used this method to convert 2 NTT in the past
I will say massivore works really well as it stinks
I've just set up 180 gallon and have 2 NTT waiting to go in there-the store owner tells me they will only eat prawn so I've got the same challenges as you to go through again