sand mate
the problem i find with using filter fool in my externals is that this increases the need for me to go into the externals and clean them up as the wool soon gets clogged and slows the flow down.
i just find it easier to access the wool from the Fluval 4+ and replace the wool maybe once every 7-10 days.
i am actually going to splash out on some polyfilter (google it if you want to check it out) and see how i get on.
It is nice to have the water clear. Its not as simple as just water changes and maintenance (although i agree that plays a big part), going that extra mile so to speak does get that little bit of extra clarity in the water.
I also noticed a better effect (clearer water) with using it in the externals. The Fluval 4+ is 1000 litre/hour flow rate, so as long as you dont stuff it completely with wool and change the wool every 7-10 days, you are maximising the flow rate and hence more water is flowing through the wool and hence more small particles get trapped, hence clearer water.... thats how i experience it
By the way, some of the guys on this forum who have huge tanks and like that crystal clear effect intentionally use internals for that polishing effect (they use polyfilter so it has other benefits too).
TIPS
--> I remove the Fluval 4+ inside trays as this allows for a bit more wool to be used without too much clogging
--> shop around on e-bay for filter fool, buy in bulk, its much cheaper
