I started with one black widow 2 years ago. That one has now turned into 15. The biggest one is the one in the middle behind the nyger trigger. When fully open it takes up 1/3 the length of the tank. I have only the black widows and mushrooms in this tank so I have moderate flow. The little ones move around all the time until they have found a home they like. Some bury themselves in a crevice as if they don't like any flow, and others prop themselves right in front of a powerhead as you can see in the upper left hand corner of the pic. I have been target feeding each one of them mysis shrimp once a week as well as the regular bits of food they catch from my daily feeding of the fish. Over the last month I have stopped the target feeding with a hope I can slow down the growth a little. They still seem to be flourishing without the target feeding. I am hoping to start selling a few of them soon. They are fun to watch and feed and provide a great movement to the tank. When ever someone comes over, this is the first tank they gravitate to. They can be mesmerizing. The only thing I don't like is my 3 clownfish still host my heater, even after 2 years!! Oh well. I have a 75 gal, 4 year old tank with 2 AI hydra 52 and FX4 canister filter that I clean once a month. I do 10 gal/week water changes using TM Pro salt. Keep your maintenance up and you will be blessed with more black widows!!