With multiple tanks - no matter what kind - your operating expenses will increase and so you kind of need to be prepared for that. SW itself seems to be expensive with all the special things it needs - I've been keeping track of Kerry and Strout. (I have not done SW and assume I never will), but with freshwater multiple tanks I've had filter, heater and light failures which needed immediate purchases. So far I have not had to buy any additives, but I have had to replace the chemicals in my liquid test kit. This is not exactly a cheap hobby, but, of course, any pet you keep comes with responsibilities that sometimes gets costly.