LC090 -- Which measuring device is suitable for the Lay-Z-Spa whirlpool?

Which measuring device can I use to best display the water values in my Lay-Z-Spa whirlpool? Do you have a recommendation?
I also have a question about problems with my water: as soon as I add Lotus Clean to the water, it takes about 30 minutes for my paper filter to seal. Is there a recommendation here?

You can measure the Lotus Clean Shock and the pH value very well with the PoolLab. For the Shock, use the DPD1 tablets.

Unfortunately, the filters in the Lay-Z-Spa are not very good. Add twice as much Lotus Clean Shock to the water and 30 percent less Lotus Clean Basic. If that doesn't help, put three times as much Shock in the water and 50 percent less Lotus Clean Basic. This will relieve the filters.

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