I made 100 pounds this summer and its in my 125 now. Im just seeding and cycling it the last bit. You can do alot of different versions ,but I got crushed oyster shells( you can also use agonite sand) at agway. 50 pounds for 8.50 and type 3 poland cement from home depot- 90 pounds for $10. You mix a ratio of 3-4 times oyster shells to 1 part of cement- mix to the consistentcy of cottage cheese.Then put the extra shells or sand in a rubber made bin and dig a shape. After you make your rock -cover it for 48 hours with more lose shells and let it sit. 2 days later dig it up and put it in a bucket of water and do weekly water changes for 6 weeks until the PH is in an exceptable range. Then put it in salt water for 2 weeks and then do a water change and then you can start to seed your rock!