Hey there Dad & Matt. It's nice to see more people coming in to or back to the SW
hobby. I have only been doing this for maybe 3 months now, but i have learned a ton from this site and from messing up and having to do things over again.. :p So if you really want great advice and amazing people to provide it as well, stick around and im 100% sure you will find that this forum has all the answers to your questions. I have not been disappointed yet..
Anyways.. enough butt kissing to AA haha.
First off, yes, indeed it does sound like you know exactly what you want to do and how to do it. But as for some suggestions:
I would skip the Crushed Coral all together and just add sand. Having a mix of both is pretty pointless and if anything will cause nitrate problems down the road. The rigidity and shapes of the crushed coral allow detritus and decaying organics to get below a certain point.. and that point is when you can't even clean it up or suck it up with a gravel vacuum. So it is not the greatest of options for a tank that will be reef in the future because coral are very sensitive to high nitrates. EVEN if you have the crushed coral in the middle or bottom of the sand bed, if you have critters like pistol shrimp or nassarius snails or anything that plays with the sand.. the crushed coral will eventually make its way back up to the surface of the sand. At minuscule amounts, obviously the crushed coral won't pose a threat, but as time goes on and the crushed coral continues to build up.. it will then cause a problem. Just save yourself the headache overall and ditch the crushed coral.
Another thing.. When putting the base rock down, make sure you have it secured in the sand properly because any shifts in the sand, assuming you will have livestock that moves the sound around, will cause the rocks to tumble over, and could become a gigantic problem that involves 75G of water all over the floor. Just make sure you really dig the rocks in the sand, but be careful not to smash the glass though
One thing you could have done if you didn't have the sand in there already would have been to put the rocks down first, and then pour in the sand. This way would ensure that nothing would get under the rocks and possibly cause them to fall. Although, you are in a very early stage of building the tank, so it still is possible to move some sand around and put the rocks in the way i said to if you feel it necassary.
Also, you said you wanted to have this FOWLR
turn in to a reef in the future correct? If so, i have a couple things you may want to think about. One thing is the livestock you buy now. Be very selective as to what animals you choose now, because if you want to have coral you can't have fish or inverts that have coral on their dinner menu. It would put stress on you and the fish, to have to take the fish from the tank and give it away all because it eats coral.. and you want a reef. I've seen it happen too many times and it's pretty sad.. for both coral and fish. The second thing is your lighting situation. For now, since all you have is a FOWLR
, that light fixture will do excellent. But the 75G tanks are pretty deep.. 21-22 inches i believe right? Unfortunately, having a 4-bulb fixture won't be enough to support a wide variety of coral. You MIGHT be able to get away with some softies.. but that is still a maybe.. not a yes. If i may make a suggestion as for what to buy as far as lighting goes.. look for the Nova Extreme Pro version of the fixture you already have. The 48" Nova Extreme Pro fixture is somewhere in the ballpark of $330-380.. It is expensive.. but with this fixture you will be able to have just about any coral you want, including an anemone furthur down the road when your tank is mature if you like those. I have this "NEP" fixture right now and it is a pretty amazing light. It has 6 bulbs and each bulb is 54Watts.. so you can imagine that's a good amount of light. My 55G and your 75G are around the same hieght, so i would definitely reccomend that fixture.
About the live rock, i would definitely suggest cleaning it off and ridding the rock of any loose decaying matter. This was one of those mistakes i was talking about in the beginning of this ridiculously long post(sorry :s). I did not clean off the live rock i was shipped AT ALL. Threw it in to my tank and i still suffer for it to this very day. My tank was unbelievably disgusting for weeks.. and is only showing signs of getting better now. That's over 3 months.. The rocks just had so much junk of them that it pretty much filled my tank and the sand.. and any time that the sand moved it expelled great amounts of the decaying matter from the rocks.. all over my tank. So.. basically it just was not fun at all. So.. yeah.. definitely clean them off.
Before you recieve the rocks, make sure you have a nice sized container to accomodate all of the rocks, and make sure the Salinity of the water is anywhere from 1.022-1.025 and the temperature is from 78-82 degrees farenheit. This will ensure that whatever is alive on your rock, will not die. This will also put you in an excellent position to clean the rocks however and however thoroughly you choose. Remember that you don't want to like power wash the rocks haha.. because you still want some organics and you don't want to kill anything living inside.
Well, i won't be mad if you don't read all this. But if you do, thanks.
Remember to come here anytime you need answers to your questions!
Good luck my freind!