Substrate and Salt Levels

If the "spotted leopard puffer" is what is commonly called the Green Spotted Puffer or GSP on the web - Tetraodon nigroviridis, or in fact any other BW puffer, you do not use salt measured by spoons, but by specific gravity. This means that you need a device which measures specific gravity. The commonest form used is one with a floating swing arm, which when filled with the watr to be tested points to a number scale with the swing arm. If the fish is in FW at the store, bring it to 1.003 - 1.005 during QT, and increase it slowly as the fish grows until the fish is water of specicific gravity of at least 1.008 - 1.015 by maturity. Some folks take the fish all the way to full SW densities at maturity, 1.021 - 1.025.

I do not understand the pH comment. BW should be at pH ~8.2, so aragonite or crushed coral is the appropriate substrate to help preserve and maintain buffering at that level. I use aragonite.

What size is your tank? GSPs are, and become moreso at maturity, quite territorial or aggressive. Two is not a stable number unless the tank is quite large and very complex visually.

Only marine mix, the material used to prepare SW, should be used for BW preparation. This needs to be done in a separate container with prefilter powerhead to allow at least a couple of days for the material to fully dissolve and stabilize before use. It can be made as full-strength SW and diluted to the correct level at time of use.

The nitrification bacteria seem to be different in BW and SW. Raising the specific gravity (no more than 0.002 per change) very slowly with ammonia challenges from FW to BW may allow development of the proper bacteria before the fish are introduced. Puffers have no tolerance for ammonia or nitrite.

HTH

I have sand and I vacume it with very little lose of sand.
I have a 36" x 1/4" straight tube and I attached about 48" of 1/4" clear hose and on the end of the hose I put a strainer.
The strainer is off the end of this Automatic Water Changer that I bought from http://www.drsfostersmith.com/product/prod_Display.cfm?siteid=6&pCatId=3884.

It work perfect!!! It catches the waste and the suction isn't that powerful that you can't control what you are trying to do.
It is wonderful because everything I want to get rid of sit right on top of the sand and it take me about 15 - 30 minutes to vac the bottom into a 5 gal pale. Then I take off the strainer and rince it out and I set the pale on top of the tank and have the water run back into the tank while I puch the tube into the sand mixing the sand up and getting oxygenated water into the sand so that good bacteria will grow.

Bacter Vital

Properly cycles aquariums by synchronizing the sulfur, phosphorous, and carbon cycles WITH the nitrogen cycle. Not exclusively Nitrobacter and Nitrosomonas dependent; also contains many other beneficial organisms missing from other products. Utilizes a multifaceted approach to nitrification/denitrification.

Probiotic effect: allows beneficial microbes to compete with and crowd out disease organisms such as saltwater ich, Amyloodinium, Aeromonas, Psuedomonas and Vibrio.
Naturally breaks down solid and soluble wastes, leftover food, and decaying plant and animal matter.
Keeps aquarium decorations and accessories cleaner.
Provides fishes and invertebrates a natural slime shield derived from marine sources. No synthetic polymers or terrestrial plant juices.
Neutralizes ammonia, nitrites, and heavy metals. Initializes and supports denitrification.
Interrupts ability of nuisance algae to nourish themselves.
Use 1 tsp. per 50 gallons daily for 3 days. Established tanks, use 1 tsp. per 50 gallons per week for 3 weeks. 4 oz. treats 400 gallons for 3 days when used as directed.

CD-361601 Bacter Vital Marine/Reef/Brackish $ 10.99

I also use the full line of Tropical Science products for Saltwater.
As a rule use FW product from 1.000 - 1.005 and use SW products from 1.006 - up.

Marine-Care Plus
Nitromax Marine
Marine-Clean
Marine-Max

Bacter Vital
Saltwater Biozyme

I also use Cichlid-Gro & Spawn-Aid every once in a while. When I use this the colors of my fish get a little more intense and my Chromides usually breed.

Melafix is what I use when ever there is any issues with my fish. It is like an instant cure (well at least I see results in 24 hours).