inline frag tank questions

[shnapper20]

hi I currently own an sps 200g tank , I do constant waterchanges using 2 dosing pumps with change 10% of my display weekly. I was looking at connecting a frag tank to the discharge doser from the display and using another doser to remove water to waste from the frag tank.
I have a choice of 2 frag tanks I could employ a 900*600*350 or a 600*600*350 both are cades and come fitted with sumps.
The 900 has a total volume of 63gal meaning it would get a 32% w/c / wk
the 600 has a total volume of 46 gal meaning it would get a 43% w/c /wk
the cost between the two isnt a lot so im not worried about the price, I have a spare skimmer rated for 200g, I have two spare hydra 52 lights and I have 2 mp40's .
Im leaning towards the 600 as I would only need one light , the w/c ratio is higher so hopefully I wont need to dose. I intend to take frags from the main tank eventually but for now am to use it to quarantine new frags and snails. I dont think I would need the skimmer, maybe some bioballs. I dont know about the mp40's I could turn them right down?
I would love to hear other peoples opinion on my options and if they think what im proposing would work. thanks john

 

[silent1mezzo]

Could you drill the tank and run the line to the drain? IMO this would reduce the risk of overflow and reduce the need of an extra dosing pump

 

[shnapper20]

No not really if i had a power outage the sump would fill and run to waste and when it came back on the auto ro topup would dilute the salinity