I have ph 7,6 - 7,7 in my 135 litre tank and even though i add PH DOWN (Aquarium Pharmaceuticals) ig goes down no more than 7,4. Is there any other way to lower it.
Fish in the tank: Two ramirezi, 1 betta, 1 catfish, 4 guppies, 1 platy and two arlekins
All other tests (NO2, No3, GH and KH) are ok