Dead F8 Puffers - What am I doing wrong?

[Ferret]

My wife and I recently (about two weeks ago) brought home 3 young (2-2.5in long) figure eight puffers. Up until now they had, we believed, been doing very well. They were actively exploring the tank, they would come greet us at the glass, and were always eagerly waiting right by the surface of the water when it was feeding time. When I fed our F8 puffers Saturday morning I couldn't find one, so I hunted around the tank and eventually found a body. Here's the tank setup:

Size: 27 galllon (hex)
Flora: Java Ferns
Fauna: 3 (now 1) figure eight puffers
Substrate: play sand and smooth river rocks (store bought)
Temp: 79º F

Chemistry:
pH - 7 to 7.2
Ammonia: 0.25ppm (It could very well have been 0, but it was off color just enough for me to bump it up to 0.25ppm)
Nitrite: 0ppm
Nitrate: 5ppm
(Note that the samples were taken after the dead fish was found in water.)
Salinity: 0.010

The water was changed on Thursday, and it was about a 50% change. The puffers' diet consists mainly of frozen (thawed in a cup of tank water) mysis shrimp. They are also occasionally be fed very young ramshorn snails. Note at this point the F8's are still fairly small, maybe 2-2.5in in length. They can't eat the snails entirely, but they do pick them out of their shells.

As the conditions above don't really scream anything wrong the only thing I can figure is the salt in the water. This was my first water change with the salt in the water. The F8's came in 100% freshwater and I gradually raised the salinity by adding about a tablespoon of salt a day until I reached 0.005. When I changed the water I added freshwater, then added salt. I overdid it a bit as the salinity was 0.010. I didn't notice this as when I measured it originally it was close to 0.005, I guess it took time for salt to circulate into the system. When I added the salt I added it by dissolving it in a cup of water, but it didn't completely dissolve. When I did the change I may have also added too little water conditioner (Seachem Prime). So for those keeping track, I pretty much did the worst water change in recorded history... The puffers seemed active and ate well prior to the water change... So I'm guessing the death is a result of the sudden increase in salinity and/or the some salt being added to the tank without completely dissolving.

After finding the body I removed some water and added fresh water to the tank to lower the salinity. I also added some more Prime to the tank just in case that was the issue. And, in the off chance that a lack of oxygen in the tank was a problem I left the water level a bit low so the HOB filter would create bubbles. I did all of this Saturday morning, and closely watched the two remaining puffers. One of the puffers seemed fine, he was actively swimming around the tank, and was responsive when I would get near the glass. The second puffer was obviously not doing well, he kept resting on a piece of midlevel decor. I fed the puffers some mysis shrimp and they both ate a reasonable amount, the stressed puffer returned to his perch shortly after eating.

When I got home from work Saturday even the two remaining puffers both seemed somewhat stressed, even the one that seemed active was now hiding in the decor a bit. I tried to feed them a little more mysis and neither showed any interest... When I woke up this morning (Sunday) to find one of the puffers dead, it was the one that seemed to be doing well Saturday morning. It was very disheartening as I thought I had fixed everything that I believed I did wrong. The last remaining puffer does seem to be slightly more active, however he still rests on the decor from time to time. He is a bit more active, and did show some interest when I offered some mysis, but he still doesn't seem to have much of an appetite.

I would really love some help with this, I'm pretty stressed over the whole thing. While I'm relatively new to the hobby, I thought (up until the borked water change) that I was doing very well with the puffers...

[J-P]

Welcome to the forum!! I'm the one that replied to your thread on TFK. You came to the right place! Too bad it is under these circumstances.
http://www.tropicalfishkeeping.com/brac ... why-67513/

[Pufferpunk]

Please answer ALL the Qs above in red.

Specifically, I'm wondering: How long this tank has been set up, how big is it & how long it took you to get to the SG of 1.010?

[Ferret]

The tank is 27 gallons (a hex as noted above). It's been set up for about two months now, and was cycled using filter media from an established tank, and tiger barbs were added to keep cycle going (they were obviously removed before the F8's were added). Water changes are done weekly and are generally around 50%. The salinity was reached over the course of about two weeks or so. Nothing else is being added to the water column outside of Seachem Prime.

[Pufferpunk]

What test kits are you using? Generally, we suggest raising the SG no more than .002/week, to keep from killing off the biological bacteria. F8s are best kept at 1.005, anyway.

[Ferret]

Using API liquid test kits. The 1.01 was an accident, I intend to keep the salinity at .005.

[RTR]

What brand of marine mix?

Brackish water should be prepared in advance or at least in a separate vessel, before addition to the tank. When you drop the salinity with FW and then bring it back up by adding dry salt, you are running a non-trivial risk of osmotic shock to the fish, which can be fatal.

The change in bacteria types from FW to SW forms generally occurs about specific gravity 1.008-1.010.. As you were at that level, you may have killed or damaged the bacteria by osmotic shock as well.

[Ferret]

Coralife Marine Salt Mix. My previous method was to add the salt to a cup of tank water, and then some time later add that cup to the tank. Assuming this little guy makes it, moving forward I'll mix the salt in a bucket and let it sit overnight.

[Dadof4]

Exactly what RTR said. I have a feeling you may have damaged your biologic filtration and the ammonia showing up is secondary to that. The reason I don't think it's from the dead fish is that your nitrates are nice and low. So the water change did it's thing and cut the nitrates and would have cut the ammonia to nothing. The salt has increased way to fast and for this particular fish, to high. Things happen, I've done stuff like that, and I think almost everyone has done something too that was accidental.

Here's an article on the easy way to mix water viewtopic.php?f=5&t=19348 Some think that I go overboard on my method but it is tried and true. Since I started doing it this way I have never had a rise/fall issue. The only thin I need to change is that between 1.010 and 1.015 the changes should only go by 0.001 as the bacteria is really sensitive to changes.

As for now, I would do 50% WC's daily and keep an eye on the water parameters. Seeing as you probably have damaged the bio filter and have access to established filter media, I would bring it down to FW over a few days and start over.

[Pufferpunk]

That article needs to be in the Library.

[Ferret]

Thanks guys, I checked on the puffer this morning and he seems to be doing ok. I'll do a water test a little later today before I do a water change.

[J-P]

These guys and gals really know their stuff! Glad you came here!

[Dadof4]

Yeah, it really should be there but there are things I want to revise on it before I put it there. I've just got to find the time to make the revisions.....