okay my bala shark and guppy just died .. i took my water to petco and they said my hardness of water was really high and my nitrates were at 80. I bought a water pillow that goes in the filter and lowers the hardness of water. How do I lower the nitates?!?! I just bought some sand from the local petstore that had seashells in it... the petco people said it should be fine...... anyone got any suggestions
