I really love sponge filters because they're SO easy, easy to clean, easy to colonize, easy and cheap to buy.
Here's an article on the filtration method that's the SAFEST for breeder fish (won't suck up fish fry)
The filtration that does the most for water clarity the soonest. The longest cleaning interval and the lowest operating cost. (No electricity except for the air pump)
And it's the oldest filtration technology there is. Well maybe “undergravel filtration” is older.