Fresh water conversion to Brackish; expertise needed

[Babsrocks]

Hi guys! Oh boy, what have I gotten myself into? Haha
I have purchased a few puffers which I've been wanting to do for many years! My little guys seem happy, eating well etc in their new 55 gal home. It is however a fresh water tank. When I got these guys from LFS they were in fresh water with aquarium salt added, so I have done the same for them in their new home. Although I know that they need to be in brackish water to continue to be happy and healthy.
I have bought some instant ocean and will start slowly bringing up the salinity to brackish. Hopefully I do it slow enough as not to overly disturb the ecological balance in the tank. What is the best way of doing this? Increase weekly? With every WC? And how much per addition? I've never done salt water/brackish water before, so I just want to make sure I do this right.

Some information:
2 figure Eight Puffers
1 GSP
2 Bumble Bee Gobies
55 gal tank
Fluval 405 canister filter (perhaps overkill for a 55, but better to overkill then under-kill, but with puffers this might not be overkill)
currently has aquarium salt 1 rounded tbs per 5 gal of water
All parameters are good, tank is fully cycled, it's been set up as a FW tank for about a year. I am a bit worried that the puffers combined with changing to marine salt may overload or crash the biological colony.
Water is soft/slightly hard (140ppm)
ph is 7.8
Alkalinity is somewhere between 100-180 (nothing in between on my card, but it's within the "ideal" range)
no detectable ammonia/nitrate/nitrite.

So what's the safest way to do this, both for the puffers and bacterial colony? I've heard that the puffers will acclimate to rapid changes in salinity as it's common for their environment, while this may be true, I know that the marine salt will kill most if not all of my beneficial bacteria, then I'd have to re-cycle the tank until marine bacteria is established. I've heard this can be minimized by slowly bringing up the salinity..... but no clue what exactly "slowly" means.
Any advice or experience would be appreciated. I tried to find an article, but was unsuccessful, perhaps my search terms weren't right. So if you know one exists, if you could point me in the right direction, that'd be appreciated too.
Thanks for your help so far!

[LilGreenPuffer]

"Slowly" means no more than .002 up per week.

There should be an article on how to do this in detail fairly soon.

[Dadof4]

When you bring up your SG, LGP is correct, you need to bring it up by .002 or less per week. Also please don't add salt directly to your aquarium.

The reason you couldn't find an article on how to do this is that the article is still sitting on my hard drive being re-written and I've been a lazy slacker lately!

Here's the basics.

Equipment needed:
1 container that is equal to 75% of the water volume in your tank.
Marine salt (obviously )
Hydrometer that starts at 1.000 or a refractometer (best investment you will make)
1 powerhead
1 heater
1 bottle dechlorinator

Process:
1.) Fill container with water equal to 50% of you tank volume
2.) Add Salt-start with roughly 1/2 cup per 5 gallons~give a stir by hand to make sure all the salt is off the bottom of the container
3.) Declorinate according to manufacturers instructions
4.) Place heater in container (use a submersible one, don't use a non submersible one, trust me on this.....)
5.) Add power head and plug in
6.) let water mix for roughly an hour
7.) Use Hydrometer or Refractometer to test SG.
8.) If the SG is what you want it to be, continue to let the water mix for about 24 hours to make sure ALL the salt is dissolved. If not add either salt to bring it up or water to bring it down.
9.) Do a 50% water change like normal but add in the newly mixed salt water.

[Pufferpunk]

"Slowly" means no more than .002 up per week.

There should be an article on how to do this in detail fairly soon.

Thank goodness for that! I'd say this Q is in the top 3 here.

The 2 BW species you are keeping have different SG requirements as adults. Please read the articles on them in our Library.

[StormySkiez]

I have never let the new brackish water sit for an hour with a heater and power head. I use instant ocean marine salt. Granted it would be best to be able to do this. Limited resource started me off mixing the marine salt with water, tested for right temp and of course declor. Then do the water change. I add half the fw then all the salt water then top off the last bit with fw. I had read on here others doing it this way.

Anyone think doing a wc like this will hurt the fish?

[Dadof4]

The reason to let it sit is that the SG can raise as the salt dissolves fully over an hour. I've seen it raise as much as .001 over that hour. Most also let the water sit for 24 hours with a powerhead and heater running to make sure the salt is 100% dissolved before it goes in the tank. Undissolved salt can burn fishes gills and if it raises in the tank it can crash the bio filter. The heater is because heat affects salinity percentage. Neal Monks has a great brackish water calculator that shows this.

[Dadof4]

"Slowly" means no more than .002 up per week.

There should be an article on how to do this in detail fairly soon.

Thank goodness for that! I'd say this Q is in the top 3 here.

The 2 BW species you are keeping have different SG requirements as adults. Please read the articles on them in our Library.

Yeah.....I had the whole article written and a beautiful graph with the all the different mixes that increase your SG by .002, when one of the kids crashed my 'puter. Had to re format and couldn't recover the article. That plus it's summertime at work...summertime + Level 1 Trauma ICU = Very busy Dadof4. I have surgery to repair my jaw next week and have 2 weeks off work after that....hopefully I should get it finished then. I'm actually trying to shoot for before surgery to get a first draft in.

[Pufferpunk]

LOL, thanks for reminding me--that's why I don't have kids!

[lilacamy931]

The method you have put Dadof4 if you havent the powerhead, do you just measure at the temp an hour later and let to stand overnight and retest same in morning? I have pump and bubble stones that can agitate water for the hour instead. Sorry to pester, just asking on alternatives

sorry to hear about the surgery and crashed data last year

[Pufferpunk]

You've got to use something to mix it. Standing overnight won't do.

[Dadof4]

Yeah, you definitely need some sort of power head to keep the water agitated. You do not need to get a top of the line $200 power head, just an inexpensive one. I have a $35 power head that I use in my small mixing container and a Mag18 (way more expensive) in my large barrel. I also use the Mag 18 to fill the tank after I have emptied 50%, gets it done in a matter of minutes (it's a man thing, bigger tools, more power...*grunt*)

[Pufferpunk]

I'm pretty sure you could find something used, really cheap.

[lilacamy931]

Ah ok guys, just checking really Next month is the investment, so will ensure to go after a powerhead!

[Dadof4]

I'm pretty sure you could find something used, really cheap.

Yeah, if you look on the for sale ads on Reef central and on craig's list good used ones can be found real cheap.