It definitely can be done. I don’t have any tanks that big, but I certainly prefer to run all of my tanks on one system because it means that I only need to monitor the parameters for one body of water, do water changes and top off on one system, run one set of filters/skimmer, etc. However, I think there are a few things for you to consider.
First, I’m assuming you’re dosing calcium and alkalinity in one fashion or another on the reef tank and not doing so on the 600G tank. If that’s the case then be aware that adding another 600G to your reef system means that you’ll probably need to bump up your calcium and alkalinity dosing considerably and that could add a lot of expense.
Second, a 90G sump might be a bit small for the two tanks. The big concern is the amount of water that will backflow into the sump when the pumps are shut off for maintenance or during a power failure. With tanks that big you may need to allow for as much as 40 or 50 extra gallons to wind up in the sump when the pumps are off and that means that you won’t have much room for water in the sump/fuge during normal operations.
And finally, you need to consider that disease could transfer from one tank
First, I’m assuming you’re dosing calcium and alkalinity in one fashion or another on the reef tank and not doing so on the 600G tank. If that’s the case then be aware that adding another 600G to your reef system means that you’ll probably need to bump up your calcium and alkalinity dosing considerably and that could add a lot of expense.
Second, a 90G sump might be a bit small for the two tanks. The big concern is the amount of water that will backflow into the sump when the pumps are shut off for maintenance or during a power failure. With tanks that big you may need to allow for as much as 40 or 50 extra gallons to wind up in the sump when the pumps are off and that means that you won’t have much room for water in the sump/fuge during normal operations.
And finally, you need to consider that disease could transfer from one tank to the other if they are both on the same system. If you have a good quarantine procedure and are confident that the two tanks are disease free then this might not be too much of a concern. If you’re using feeder fish of questionable health in the predator tank then there’s a bigger chance that the health of the reef tank could be affected by something in the predator tank.
Re nutrients for 600g, I disagree. Certainly getting levels right on 600g more will use more dosing, but having more volume doesn’t mean the rate of usage goes up proportionately. You might just have to get 600g to match and after dose close to the same amount (discounting coralline or other additional growth in the predator tank).
