"I bought the smallest size of this product so that could clean out the waste from my Betta's gravel without having to remove the fish and dump all the water.
But once I started using it, I quickly found out that, with my 1 gallon tank, I had to add water while syphoning so my fish wouldn't be left high and dry. It did remove some waste, but the fact that I had to add water made it extremely impractical. I would have been better off removing the fish to another tank, dump the water, clean the gravel, add new water, and put the fish back in.
I would NOT recommend this to anyone who has a tank of volume less than 10 gallons."