How about this for filtration?

[dwarfgourami7]

I have 3 tanks; 30 gallon(fluval 3+ filter), 18 gallon (fluval 2+ filter) and a 3.6 gallon (fluval 1+ filter). I got a fluval 205 yesterday and will be setting it up at christmas so then i can move the filters down a tank (3+ going to 18 gal, 2+ going to 3.6). So i guess thats pretty good filtration as all the filters are well under their maximum limit! YAY!!

 

[amosf]

I'd run the new and old filter on the big tank together for a couple of weeks to get the new one established, then do the filter swapping...

 

[dwarfgourami7]

Yeah i planned that. How long before i can take the current filter out of the 30 gallon once i connected the external filter?

 

[webcricket]

Give it at least a couple of weeks (14 days). When you do remove the old filter, be sure to test your water a couple of times a day for two or three days after to be sure you're not seeing a mini-cycle.