So I'll chime in here as I normally just read a lot but don't write back much. My display is 1000 gallons plus another 500 in sump/grow out. I've been through it all, algaes, ich, and an almost complete crash due to a simple refractometer out of calibration. It was a rookie mistake made by a 20 year hobbyist. So the following is in no particular order.
1. Plan, Plan and then look at failure points in your plan. Easier to account for bottlenecks and failure points on paper.
2. All equipment will break or fail at some time so have a backup ready to go. Heaters, pumps, lights not as critical but no heat and no flow equals failure.
3. Consider the fact that in large "stable" water volumes issues creep up very slowly until they reach a critical mass. If you're not careful in checking your water parameters things can go south quickly. It's not even close to relevant on performing a 50% water change on 1500g like it is on say a 180g tank.
4. You don't have to buy the most expensive equipment. You need to buy reliable equipment that is readily available.
5. Take your equipment list and calculate how much energy costs are going to be. I've seen people set up large systems, spend lots of cash, and then have their jaw hit the floor when the monthly utility bill arrives.
6. I would recommend a Triton method, ReefMoonshiners, or whatever trace element ICP combo you prefer because for me it's way cheaper in the long run than water changes.
7. Ozone is your friend.
8. The last thing I would add is your level of control and automation. This one hits me personally so I'd like to share my thoughts with everyone. When you have systems this large I would advise against using hobby grade control packages. I have had my Apex fail three times in two weeks. Flat out failures, no alarms sent, just really lucky I was home when it happened. They system said everything was fine, but all the power was off. I'm not going to say what company failed, you can PM me for that info if you want because I'm not throwing them under the bus here. It's just that you need to be aware that hobby grade is just that, it's not an industrial platform. When you total the amount invested in tank, gear, and livestock you owe it to yourself to build or have someone build a Programmable Logic Controller. I'm doing that now and I'll never ever go back to hobby grade. So far the cost of building it is a little less than a full blown system with multiple control bars, modules etc etc. In my field we use PLC's to run industrial, food, biotech plants and they work. Again, it's not a negative towards the hobby grade equipment, but is it worth losing thousands of dollars of livestock over controller?
9. Coming back to reliable equipment, we all know that if it's made for a niche
market you pay a premium. Do a little research and you can find equipment that works just fine for aquarium use that is made for another bigger
market.
I could go on, but I'll stop there for now. Good luck with any new big tank build, I love mine even with all the ups and downs.