I have a 75 gallon tank, its usually around 65 degrees. Ph of 6.5-7, canister filter and drip/overflow system of .5 gallons an hour. There is some flow, but its not overwhelming. It has a bubblator, and 2-3 millmeter gravel, as well as a mix of real and plastic plants, and several hiding places. Would a weather loach get along with the shubunkin goldfish and be happy with this set-up? What about a common/comet(wouldn't it get to big)?