Lol. So three out of seven lets be easy and say 40%. Math isn't my thing. My husband who understands all that sorts stuff had just said watch the water so it doesn't overflow said I got it. Yea my one gallon overflowed and he tried so hard not to laugh at me. Didn't work. So we got the old three gallon tank and it was about half way full. Needless to say I didn't have three gallons ready only one so I put that in the tank and then made a another batch of water. Why do water changes when I can just vacuum my tank out? Seriously. Would it be ok for me to vacuum it out every third day or does that stunt bacteria growth?