Need advice setting up GSP tank

[PHLGSP]

Hi, new to the forum and excellent information I've read so far. I'll try to make a long story short. Getting back into aquariums as I always had one as a kid. Bought a 5 gallon Fluval Chi, cycled it and planted it heavily (it is near natural light so it does well despite the poor lighting it comes with) and wanted to stock with a single fish. Did all my homework ahead of time and decided on a Dwarf Puffer. Get to the LFS (not a big box store) that supposedly specializes in small aquariums. They're out of Dwarf Puffers, "but hey, look at these Green Spotted Puffers the care for them is the same and instead of growing to be an inch they will grow to be 2 inches" I was told. So, I should have hopped on my iPhone but I didn't and I headed home with a GSP.

By that evening I knew I needed to return the fish, or prepare for quickly moving to a larger tank. I decided to keep the GSP and get a larger setup, and in the meantime do frequent water changes and start transitioning to brackish. Its been a few weeks and I'm at 1.005, plants are hanging in there, fish is doing well and water quality is good.

I am now planning the next tank to buy and set up in a week or two. I'd like some input from GSP veterans if you don't mind. My plan is for a 30 gallon (can't go any larger unless it is the 37 gallon and I'm not too thrilled with that depth) with filtration for at least 70 gallons. Here are my specific questions...
- heavy brackish or marine?
- if heavy brackish what is the best live filtration? Any success with live rock or plants?
- if marine, this would be my first full saltwater tank and I don't want to attmept reef. With FO or FOWLR could I use tap water that is filtered (refrigerator charcoal filter) and treated with Prime (or something) or is it a MUST to use RODI water? I want to avoid RODI due to contraints on where I would put a unit. The wife is not thrilled that my 5 gallon on the nightstand is turning into a 30 gallon on our main floor.

My preference would be marine FOWLR but not having to deal with the RODI unit. I'm trying to plan this for optimum success and not having to redo it down the road. Any insights are greatly appreciated.

[LRU]

I use regular dechlorinated tap water even on my reef (24g nano) with few to no issues. So, in my opinion, RO/DI is not a must, especially for a FOWLR.

I'm not 100% certain but if you buy live rock and then plop it in a brackish tank it will probably kill all the marine bacteria.

You can work your way gradually up from fresh to marine by aiming for .002 salinity change per week, in order to preserve the bacteria colony. I've been doing this with my GSP (but more like .002 every few weeks) and it's up around 1.006 right now.

Or (have not tried this but friends I know have, plus people here on TPF) you can start with full marine in the new 30g and acclimate the GSP over a matter of hours via drip acclimation or pouring a cup every 20 minutes or so until you get the salinity from his current up to marine salinity.

[Pufferpunk]

Most of us use Prime for dechlor.
Here are some articles for you:
library/puffers-in-focus/an-introductio ... d-puffers/
library/water-filtration/fishless-cycling/
library/water-filtration/emergencycycle/
viewtopic.php?f=8&t=19348

[PHLGSP]

Set up a FOWLR using tap water, cured live rock , and cycled it quickly with BioSpira and Stability. Dripped the GSP from 1.005 to 1.025 over the course of several hours. He is doing great.

Thanks for the input on using tap in your reef. I'm going to try a nano reef in the chi. Since it's so small I am just buying distilled water for it. Have just added LR and am fast cycling it. Maybe the same LFS will send me home with an adult dog faced puffer for it this time. That's a joke. Sorta. At least I know to use my iPhone from the store to question anything!