From birthworks website:
Water Maintenance Kit
If water is kept in a pool for more than 24 hours, bacteria and algae begin to grow in the water. To counteract this, we offer a water maintenance kit for use with the BirthWorks heater unit.
This is the system you get with a Gold Option or the Diamond Option.
It's made up of a filter chamber with a filter element and a spa system of tablets and liquid used to oxygenate the water to prevent bacteria multiplying in the water. There is no chlorine or bromine content.
At BirthWorks we pioneered this system and have used it for over 15 years. Thousands of babies have been born in this way (including our own) and we offer it as an option with complete confidence in its safety and suitability for water birth.
The Active Oxygen sanitation systems comprise of two components that are easy to use and work synergistically together to keep your water free from bacterial growth and algae.
The Active Oxygen Activator Liquid
Bayroplus is a liquid that is a long-lasting activator which should be used weekly in conjunction with the compatible Active Oxygen Tablets to activate the disinfectant effect of the tablets and prevent algae growth.
The Active Oxygen Tablets
Bayroklar are quick dissolving tablets that should be added to your water on filling the tub and then prior to using, or weekly if the tub is not used. The tablets destroy bacteria and remove organic impurities.
Both are chlorine and bromine free, working similar to pond plants by oxygenating the water.
Using this system means it's safe to keep the water in the pool for weeks at a time.
The tablets are high in alkaline and, if you are use quite a few of them, you may find that the water appears cloudy, If this happens it would be advisable to change the water.
You may also find that if you live in a soft water area the water can get cloudy, again in this instance you would be advised to change the water weekly.