I have a bromine hot tub that I am having a hard time keeping any bromine level available. I am using MPS to shock and adding bromine granules. I have the spa frog system but haven't really been using it as I was advised that it was not very effective on this forum. My question is: Can I use the bromine cartridges as a floater to keep my bromine residual up? Is there any advantage of using the mineral cartridges? I have about ten bromine cartridges left and three mineral cartridges left. I hate to let them go to waste.

I wouldn't use the mineral cartridges at all. However, as long as you already have the bromine cartridges you might as well use them. They will help, though it may or may not be enough depending on what is really going on.

If I shock with MPS the bromine levfel goes way up but drops to 0 in several hours. I thought I would use two of the bromine cartridges on the frog floater instead of the mineral cartridge. Am I not keeping enough bromine reserve in the spa, or am I not shocking enough? How do I determine what to do?

If your bromine level is going way up you have a good bromide reserve. The fact that it is falling quickly means there is something organic in the water that it is breaking down. You need to keep reactivating the bromine until you can maintain an bromine level.

As a very rough rule of thumb, for every person-hour of soaking in a hot (104ºF) tub, you need to add 5 fluid ounces of 6% bleach or 3-1/2 teaspoons of Dichlor or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize the bather waste. Since you have a bromine spa, adding any of these oxidizers will create bromine that will do most of the real work. Many people simply use too little oxidizer to handle their bather waste. By the way, these amounts assume you have no ozonator. With an ozonator, you need less -- perhaps half these amounts.

At this point, you might be behind in oxidizing your bather waste so will need to use more to catch up until you get a consistent bromine reading.

I do have an oxidizer.

Should I add MPS if the tub isn't used over a period of time? Or just after use?

New Marquis Euphoria that has inline spa frog system and ozonator.

Why do you suggest against the mineral cartridges?

Im looking for an easy and cheaper way to keep this clean, it is heavily used and will continue to be so year round. The cartridges are very pricy.

Right now my bromine comes in at 2ppm as suggested by the spa manufacturer.

I think you meant ozonator. You add the bulk of the oxidizer right after a soak. That will handle the bather waste from that soak. As for whether you need to use any in between soaks, that depends on the bromine level your ozonator is able to maintain since the ozonator will oxidize some of the bromide bank into bromine. So you'll have to measure the bromine level in the days in between soaks to see if the ozonator is keeping it up high enough -- somewhere in the 4 ppm bromine range. If not, then you'll need to supplement with an oxidizer though probably not that frequently -- perhaps once or twice a week when the spa is not in use.

You may find that to keep the water clear you need to use chlorine (such as 6% unscented bleach) as your oxidizer on occasion, perhaps every other week. Ozone and bromine and MPS work OK and oxidize some things better than chlorine but there are some things that chlorine oxidizes better.

You are right. I had oxidizer on the brain!