I'll help you out doresy, I fully understand all your post's and what your getting at. Unfortunatly I'm have trouble posting in the members photo area so I'll just do it here. I will try to stay away from the obvious and what has already been pinned in certain areas of this form, as far as general care goes. Instead I'll try to stick to more personal experiences. All photos will be posted below.
First off I bought both of my Green Spotted Puffers (Tetraodon nigroviridis) from walmart of all places, rescued is probably a better word for it (they were quite sickly when I got them). They were only 1" and 1.5" in size, one has always been a lot bigger in size than the other one, like the small one was the runt of the family or something (in the wild the small one would surely have died early on). So I brought them home at put them in a 10gl as it was the only size tank I had at the time that was empty. They stayed in that tank for approx. 6 months time, then were move to a 30gl tank. Now they are housed in a 52gl tank (I originaly thought it was 48gl, after some precise measurements and math found that to be wrong).
I have never had any aggresion problems, I could be just lucky. Here are some pointers I have learned through the 3.5 years I've owned them and how I care for mine.
1) If you want to keep more than one puffer in a tank, get them all at once and at a young age
2) 30% water change twice a week with gravel vac.
3) Every time I do a water change I change the decor around
4) I fluctuate the sg. levels during every other water change
5) I always stock the tank with 15-20 ghost shrimp every week
6) Everyday I take a very close examination of the Puffers and look for anything unusual in swimming habits, skin color, eye color, fins, teeth, and anus area.
7) Feed them snails often and treat with bloodworms
8 ) Lights on 1 hour after sunrise and off 1 hour before sunset all year timing with the seasons.
9) I fluctuate water temp. with the change of season as well
10) Here is how I increased the sg. level with age
very young (acclimation period after store bought) 1.000 - 1.002
young (1-3 months) 1.002 - 1.006
adolescent 1 (3-6 months) 1.006 - 1.010
adolescent 2 (6 months-1 year) 1.010 - 1.014
adolescent 3 (1-2 years) 1.014 - 1.018
adulthood (2 years+) 1.016 - full marine
Some may say this over board and a waist of time. I on the other hand believe in trying to imitate the wild as much as possible. I do not know the sexes of the Puffers but I am going to try and breed them anyway. To do this I will be removing all the current decor and replacing with live rock and bring the sg. up to full marine. I will leave it this way for about 2 years. After 2 years I will lower the sg. level back down rapidly to freshwater (1.000-1.002) in a 3 month period and replacing the live rock with true mangrove roots and other live plants from there natural habitat. By then I will have at least 4 more GSP's on hand to swap out during the experiment.
I would say if you want GSP's you could start them out in the prospect tank then you may have to move them to a larger tank within a couple years but GSP's are well worth it.
Wheeew, that was a lot
I hope this what your looking for. Here are pics.
If anybody has any Q's just ask.