How many hermits is to many??

cool, you might just regret saying that :D .....ok totally straying from the subject of this thread but...an RO unit is the next thing on my shopping list of expensive goodies, as my LFS does 25l bottle of salted RO water for £8 is it gonna be a big saving for us to get our own unit and make our own. its a 240l tank so probably be wanting one bottle £8 per week. if getting our own is a good saving long term which i guess it is? what type size etc do i need. thanks.
 
ok any good links of shall i check out e-bay? saved a fortune with my powerheads there compared to lfs, feel a bit guilty not buying my stuff from them though as there really nice and helpful but.....there is a recession
 
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