Hmm that doesnt seem like a big dollar difference BUT keep in mind if you get the larger one and tone it down then you are still using more electricity than if you get the wp40.
I don't have the wp40's even at full blast in the 180g, they are about half way up.
In this case the extra $2 might be a waste in my opinion.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.