Great thread all day!!!! Here is the thing in my opinion brotha you need ample rubble rock and stocking your tank with a bottle of tigger pods is a good way to boost and increase the food count for these little guys , also if you have any other fish like wrasses that eat pods as well , you gotta keep your eye on the food balance.
The pile of rubble rock is in fact a very good idea , also rubble rock in your fuge helps also and yes they can make it through the foam filter at times and also when you change your sump sock , try to do it at night and shutdown your skimmer and let the water flow directly into your sump so that some pods can make there way back Into the sump .
You will see them in your filter sock squirming around so dunking your sump sock in the sump can help keep your count up.
Last but not least every few days , turn your light on in the middle of the night and you can see the pods running all over the place, ( or use a red light ) and this will give you an idea as to whether or not you need to restock your pods .
This is just info I have gathered from when I had my mandarin , I hope it helps.