I put about an inch of potting soil on bottom, then stuck about an inch to inch and half completely covering the soil, I filled it with water using a plate to buffer the water stream and it filled up fine, but as soon as I poked a hole down to the soil to stick the plant in the potting soil just shot up and clouded the whole aquarium to where you couldn't even see through it. I let it sit for several hours and it didn't settle any, was still just as cloudy with some big pieces floating on top. I even stuck a 10 gallon rated HOB filter in there to try and clear it but it kept clogging up the filter.
I researched for literally at least two weeks before attempting a dirted tank. So at least I kinda knew what to expect: Keep in mind that my fish were in my 29g tank during this process and I am talking about dirting a 75g tank, so with your size tank this whole process should be a walk in the park.
I would have loved to use fluorite but for a 75g tank it was more $ than I could stomach.
First, I triple rinsed my organic garden soil (I used 2 1/2 bags at about $7 each) in a 5 gal bucket to get as much of the really fine particles out. I did this outside but it was still a messy process. Then I put the soil in when it was still pretty wet, this was something that I learned would make it easier to get it to compact down and reduce the amt of floaters I would get. Then I put about a 1" gravel cap on it. Rivercats recommended adding another inch of gravel cap which I did later because I was still getting a good number of floaters pop up daily. This extra cap thickness was the trick... thx again Rivercats. And yes I did thouroughly rinse my gravel before putting it in but the water was still cloudy.
Based on another recommendation on an initial setup of a dirted tank I then did about a 80% water change every day for about 5 days. This was a PITA because it is a 75g tank after all. But this helped get a lot of the cloudiness out but it was still cloudy. I learned that this is still "normal" but that it would go away in about another 5 to 7 days. Even though I didn't think it would ever clear up it did, and I mean crystal clear after about another week. It was this week, the second week that I started running my canister filter (with carbon).
Floaters: I just used my small net to remove them from the top each day for about a week. Each day I had fewer and then after about a week I had none at all. Then I added some more plants to the tank and each time even though I was very careful I would get 10 or so floaters pop up to the top, which again I just used my small net to remove them, took all of about 5 minutes.
So yes, my water was really cloudy too even after my daily 80% water changes that I did for a week, but then after about another week my water was crystal clear. Other than a very recent alga problem I am having (probably not enough CO2 and possibly too much lighting) I couldn't be happier with how the dirting process turned out.
CO2 thoughts: I am a newb here but here is what I do know. Your plants must have CO2 to survive and grow (needed for photosynthesis). They can get CO2 from: #1 your fish if you have enough fish, #2 a CO2 system as long as the CO2 actually gets dissolved in your water, #3 from water you add to your tank. The water you add to your tank is going to have some dissolved CO2 in it, just as it has some dissolved O2 in it. From what I have learned CO2 is easily released from the water (i.e. no longer available for your plants) if you have too much surface agitation.
If you don't have a heck of a lot of plants in your tank your weekly water changes might provide your plants with enough CO2 since your tank is relatively small.
On the gourami note, I have had a dwarf neon gourami in my 29g tank for about a year. Then I was "sold" another dwarf gourami by one of the workers at one of the big box pet stores. I really didn't want another but was looking for another colorful fish and he told me that gouramis are community fish and "easily get along with each other as well as other fish". So I put the other male gourami in my 29g tank and the war began. I thought the bigger one was going to end up killing the smaller one. I moved them into my newly set up 75g tank earlier than I wanted to put fish in it, but when I did the fighting stopped, they seem to be tolerating each other now. One stays on one side, the other on the other side. When they feed they interact but for the most part just ignore each other now. Seems that in a bigger tank they were not stressed out anymore.