Transcript of Heart Disease and the Excretory System. Heart Disease and the excretory Heart disease slows the oxygen flowing throughout the body. So oxygen moves slower to the excretory system.
The most likely causes of a shift in pH are: 1  Something in the water source buffering the water. 2  Something in the tank buffering the water. 3  or Something you are adding to the tank.
Water Hardness & pH Levels. Water hardness is often confusing and therefore overlooked by many aquarium owners, though quite important because it is closely related to pH levels. Fish can only thrive in certain levels of water hardness, and if the levels are out of balance, it can cause stress and death.