Fluid is a big thing for Patrick and I'm convinced Patrick's stone formation accelerated when I stopped his addition fluids. I've been doing some reading and was intrigued to read the PDSA state a guinea pig should drink 100ml's per kg! Source: http://www.pdsa.org.uk/pet-health-advice/guinea-pigs/diet#water-for-your-guinea-pigsnbsp How much water should my guinea pigs drink each day? The average amount of water a guinea pig drinks is 100 to 200ml per kg bodyweight per day. I had read previously 100ml's per kg on GL - in stone prevention so for Patrick I aim to get between 60 - 90 ml's into him daily as he weighs 900grams. My healthy guinea pig's don't drink anything near this! I was curious to know people's experiences who have had bladder stones removed - are your bladder pig's big drinkers?