TetraEasyBalance 8.45 Ounces, Weekly Freshwater Aquarium Water Conditioner, (Model: 16177)

Q: can i use this in a 1 gallon tank?

Yes as long as you adjust the dose. Should be 1/2 ml per gallon or 1/10th of a tsp.

Q: Is it suppose to make the water cloudy?

It does at first but clears up within a few hours.

Q: Can use it for just treating hard water when all my other levels are good.

Not if you are hoping to lower the hardness. This product was designed specifically for people who tend to do infrequent partial water changes. When water changes are not often enough, organic matter drives down the pH and hardness. This product helps to add buffers and bring those levels back to within a good balance. It will prevent hardness from dropping. To soften water, add aquarium safe driftwood or mopani wood.