Yeah I might try that and it has also been suggested I add a little cider vinegar, not enough to taint the water and stop the rats drinking but it inhibits the growth of the algae.
Thanks everyone.
Thanks everyone.
TrueBlue said:I used to have this problem, but now any bottles that are exposed to sunlight are covered and the problem disapeared over night. I use plastic ice cream tubs or simular to cover the bottles. Works a treat.