Hello, and a quick Brackish FAQ update

[nmonks]

Hello all --

After about a year of lurking, I finally subscribed and wanted to say hello to everyone here. It's been a pleasure learning from so many erudite and experienced aquarists.

One thing I did want to mention is that the web address for my Brackish FAQ is not the one that seems to be used here. That version is on an old ISP and hasn't been edited for many years. The correct address is below. The puffer section isn't big, but it has been substantially changed over the last few years. I think you'll find many of the errors in the old version have long since gone. The FAQ has been evolving over ten years now, and depends a lot on people sending me information. Comments and corrections from anyone on this forum are happily received and will be credited.

http://homepage.mac.com/nmonks/aquaria/ ... aodontidae

Sincerely,

Neale

[RTR]

Welcome to the site, Neale.

Re the BW FAQs and f-8s, I have long wondered about the lit reports on these fish, but have not searched out the origionals to see what if any water specifications are given. Due to their apparent "need" for light BW but apparent inabilty to handle high BW or SW I would love to see TDS figures on their reported habitats. I have long suspected that elevated TDS, especially KH, may have more significance than the salinity. But I was burning out on water mods and did not start another test series to explore that aspect. T.bicellatus is one of the easiest puffers to ID in live fish - they either are or they aren't. Don't we wish they all were as so easy? I don't see mis-ID as a big issue there, although "giant" f-8s do still get reported (read as: more or less stunted T. fluviatilis).

[nmonks]

Re: figure-8s -- brackish or not -- I think the problem here is one with brackish fish generally. What we create is a fixed environment with one salinity, because that's what the filter bacteria need.

But in the wild, these fish are exposed to changes, they've adapted to deal with changes.

The few times I've read or spoken with people who have spawned difficult fish, like monos, scats, and garpike, they've either kept them at the "wrong" salinity or been moving them between fresh and salt. A few months ago, someone wrote to me through PFK magazine about how to raise the eggs his monos kept producing. They'd been keeping them for a couple of years... in fresh water!

Now, no-one would recommend anyone do that, and yet when fish are breeding, then you're on to something important.

Obviously with brackish water fish life is a lot more complex that simply saying such-and-such a specific gravity (or pH, or hardness) is the issue. It might well be that figure-8s the fish spend 90% of the time in freshwater, and only sometimes get caught up in the salty water end of the estuary, but that 10% of the time is critical for their health. Perhaps they top-up with minerals or re-set their sodium/potassium levels or goodness knows what.

As I've said before, figure-8s are fish I've never kept, so I don't have any personal experience either way. My first brackish water puffer was Arothron hispidus, bought from a tropical fish shop in Dundee, Scotland, that had about twenty of them in a freshwater (yes, freshwater)
tank. A very nice fish, and seemed to get along well with monos, scats, etc.

Cheers,

Neale

[monsterpuffer]

It might well be that figure-8s the fish spend 90% of the time in freshwater, and only sometimes get caught up in the salty water end of the estuary, but that 10% of the time is critical for their health. Perhaps they top-up with minerals or re-set their sodium/potassium levels or goodness knows what.

Given that the SG recommended most of the time for F8s is 1.005, which is on the low side of salinity, do you think that its possible that rotating the SG may be beneficial for a fish like an F8 or any brackish fish. If your SG is at 1.005, and your doing weekly 50% WC, maybe not add the salt for two weeks and then come back on the third week and week by week ramp the SG back up to 1.005 and then back down again, so on and so on. If done properly you wouldn't stress the fish too much - maybe a smaller WC may be in order or a 50% WC with adding not as much salt to lower the SG slowly.

I'd try it myself but my last F8 recently passed on and I've got no other fish that are brackish. I actually just ramped up my GSP to 1.019 this last week.

I think part of the problem with breeding the brackish puffers (or puffers in general) is that their environment is so fluid and always changing that no one has figured out the triggers that initiate mating (as far as I know anyway).

My brain is fried this week due to a lack of sleep so I may be spouting gibberish.

MP

[nmonks]

More often than not, varying the salinity does brackish water fish no harm, and often does some good, either triggering breeding behaviour or else surpressing external parasites. If you want to mimic the wild, then varying the salinity (maybe even twice a day!) would be the way to go, exactly as you say.

But... your filter bacteria won't love you for it. And there's the rub. If you filter starts dying, then it doesn't really matter if there is a small positive to varying the salinity, the big negative of a nitrite/ammonium spike will outweight it.

Hence, we have the ecologically nonsensical situation of keeping brackish water fish in a fixed salinity, and the inevitable result that very few of them have been bred yet.

Cheers,

Neale

[RTR]

BW fish kept in tanks are not exacty jellyfish in the tides. By and large they can selct the density or at least the gradient that they want. The puffers may be the least adept at that selection based on their lack of sustained speed swimming.

Long ago I did vary my salinity by small increments or slow dilutions, But when I wnted to play with lifespans, I selected fixed densities and held them to simplify things. After that I never woried about variation, but I also never attempted breeding BW puffers.

The fellow out in CA breeding Monos does use FW/light BW. but my understanding was that he moves the fish rather than changing the water in a given tank. I have no clue as to the rate of change he uses. All the detail I got was second-hand at best, so not particularly reliable.