Upgradation of my existing tank

Question
Hi Paul,

I am confident that you would be able to answer my questions. I am upgrading my 75 gallon tank to 125 gallon tank very soon. The tank is ready. I have had the 75 gallon aquarium for 8 years. It is a thriving semi reef tank with a few anemones, SPS Corals and fish. I have not overcrowded the tank with corals as I believe in giving space to existing specimens to grow. They are doing good. I am using 20k metal halide with a few 10k compact florescent tubes. I have 70 kg of live rocks. Have plenum filter currently that works in tandem with a 30 gallon sump which has various stages. I use active carbon, zeolite, ceramic rings, bio balls and few highly porous live rocks as filter medium. The flow rate rate is awesome and the display tank has good water movement. I do not use synthetic salt to prepare water as we have access to Indian Ocean. Now the situation is I do not want to set up a plenum filter for my 125 gallon tank that means I am not going to have a thick base medium. Earlier I used to have crushed corals as base medium but this time I am trying really hard for live sand. The problem in India is people are not aware of these things and are ready to compromise with the equipment, and other various important stuff. Everything is in place but I was unable to find live sand for my tank. The question was can I use plain sand for base medium mixed with crushed corals from my old tank so that it can kick off the beneficial bacteria? I was willing to have a 3 inch sand bed. Do you suggest me to have a wavemaker or a few tank janitors to solve the purpose? In India we do not have access to sophisticated equipment because there is no demand here. A few friends of mine were suggesting me to go for a UV sterilizer. Do you really think it is necessary as I am going to add another 60 kg of live rocks to the display tank and 5 kg to the sump? I thought live rocks were the best when it comes to filters. I was also willing to get some caulerpa for my sump. Does it need a strong light with high Kelvin rating to flourish? Apologies for pestering you with so many questions. Please put some light on these concerns. Your valuable guidance will appreciated. Will keep you posted on my tank related advancements.

Regards!

Answer
apologies for the delayed response, work has kept me very busy.

any sand that will be seeded with your old sand will eventually become live, just a matter of waiting it out. if your using natural sea water i think it would defeat the object to use a UV steriliser, i think you are very lucky to have such a fantastic natural resource near by.

if you want to have a deep sand bed you can use a seperate compartment in your sump and fill it with sand for the anerobic bacteria, coupled with the extra liverock it sounds like its going to be a fantastic setup!

caulerpa will be fine with moderate lighting, a 12Watt white T5 tube will be fine.

please keep me updated on your progress, i am always interested to see how peoples tanks come along.