For planted tanks, pearling effect is like the "must have" effect..well for a newbie its very satisfying. However after a while, its quite normal-lah... There is no need to see pearling, as long plants and fish are healthy is good enough for me.
Some people complained " I spend tonnes of money and time but there is no pearling!!! Help!!" well no pearling is not end of the world, it just mean to O2 level is not high enough. You need the tank water to be saturated with CO2 + your plants are creating additional O2 to get the effect.
To achieve pearling, you need to fulfil the following:
1) Sufficient and high Levels of CO2(30ppm and above) you can use a drop checker to check, minimum green to yellow status should be good enough.
2) Sufficient Fertilizer, you have to dose regular fertilizer. I find plants will pearl readily if there is sufficient fertilizer
3) Lights: need to have high level lights if you really want to see good pearling( 3-4watts per gallon) and your tank should not be too tall or your lights will not be able to reach the bottom or low laying plants. I would suggest max 40cm tank with 6500k light tubes. See my following experiment: http://theplantedtankblog.blogspot.sg/2012/03/upgraded-to-4-x-t5ho-all-aquazonic.html
4) Types of plants: some plants pearls faster and better e.g HC and Riccia. I manage to get java moss and US fissiden to pearl too.
5) Surface agitation: keep to low, too much water flow will blow the tiny pearls around and you might not see them.
6) Temperature:keep to below 30deg celsius
Finally if all above does not work, OFF your filter!!! Power up co2 /lights and wait for 2-3 hours.... You should see some pearling.