Buying Tank For Brackish Aquarium - Advice Please

[jenny6165]

im going to buy a 70 litre tank (18 US gallons) for a brackish setup to house hopefully a figure 8 puffer.


do you set it up the same way as a freshwater aquarium?
i know ive had a thread like this before, but as i should be getting the tank this week, i wanted to be sure of what i needed to do.
Could i use 50% of my freshwater tanks water to help set it up, or is this pointless.
Also, when i do the cycle, do i start with normal water, wait for it to cycle, then add marine salt. or do i mix it up first, then cycle?

 

[MoMa]

Mix the salt and water first. Neale Monks has a handy program for measuring the amount of salt you need here.

The bacteria in a brackish tank are a bit different than that of a freshwater tank, so as long as nothing else is housed in the tank yet, start cycling with brackish water. Using 50% of your freshwater tank's water probably wouldn't hurt, but adding the marine salt would kill off most, if not all, of the beneficial bacteria.

Also, did you purchase the tank yet? It's just a hair under the minimum recommended size for housing Tetradon biocellattus. Upgrade if possible.

cheers!
MoMa

 

[jenny6165]

hi there,
i found a 120 litre tank i can fit in, so am going to get that one i think

 

[nmonks]

I'm going to stick my neck out a little here, and suggest an alternative to the excellent advice MoMa gave above.

Figure-8s can live for months, even years, in freshwater and a few weeks in freshwater will do them zero harm at all. So, instead of setting up the tank at SG 1.005, set it up as a freshwater tank, and install 50% of the filter media from your other aquarium. The other aquarium will quickly re-mature any new medium you put in its filter (literally, within days) and the new aquarium will be effectively mature from the get-go. By all means add some water from the other aquarium if you want, but it really doesn't make much difference. What matters is the filter medium.

You can now install a figure-8 pufferfish and be confident that the tank will be stable. Don't overfeed, and do watch the nitrites, but really, nothing should go wrong. Once the pufferfish is in the tank, do a water change of 10-20%, adding brackish water at SG 1.003. This will have no effect on the filter bacteria at all, because the salinity of the entire tank will be extremely low (less than SG 1.001).

Over the next few weeks, do similar changes, raising the salinity in the tank little by little. The filter bacteria will adapt without any problems, and after a month or so, you should have a tank at SG 1.003, which is an adequate level for figure-8 pufferfish. Once you're happy everything is working, you can then nudge the salinity higher by adding SG 1.005 at each water change, and again, the slow change will allow the filter bacteria to adapt.

This approach works well with any low salinity brackish species because the filter bacteria in freshwater and at SG 1.005 are almost certainly the same (SG 1.005 is, ecologically, practically fresh water and you'll find mostly hardy freshwater fish and plants in such regions). The problem comes when you go above this level, and by SG 1.010, the filter bacteria may well be more like those in marine tanks.

Cheers,

Neale

 

[MoMa]

To be honest, Neale's advice might be a bit better than mine, if only because it's more than likely any Figure 8 you purchase is being housed in Freshwater at the LFS. Starting w/ freshwater will eliminate the need for any "slow-drip" acclimation for the fish.

I think the real key is raising salinity slowly.


I got lucky when I purchased my GSP. He was housed in Brackish at the LFS, and that's why I cycled my tank brackish.

 

[nmonks]

Not really better advice, but with figure-8s and one or two other species you do have some latitude because they can do well in freshwater indefinitely (or at least for several months/years). My advice would be bad with, for example knight gobies, violet gobies, green chromides, scats, monos, GSPs, etc. For these, you really do need to start at 1.005 or more, and mature the filter as brackish from the start.

To be honest, I feel the slow drip method is a bit molly-coddling for many brackish water fish. Depends on the species of course, but many can be taken from freshwater to marine within an hour or so (done this many, many times with mollies). They've evolved to do sudden salinity changes. Scats, for example, even as adults, swim freely between rivers and the sea (contrary to the myth scats do not "grow up" in freshwater and then "swim out to sea" as adults). Schaefer, in the Aqualog book, even says you can dump a scat from seawater straight into a freshwater tank without any problems. I'd be a little kinder, and give the fish an hour to adapt in a bucket, but still, these fish aren't nearly as bothered about salinity as we sometimes imagine.

On the other hand, some species, like guppies, can only be taken between freshwater to marine over really long periods, ideally a week or two.

Cheers,

Neale

To be honest, Neale's advice might be a bit better than mine, if only because it's more than likely any Figure 8 you purchase is being housed in Freshwater at the LFS. Starting w/ freshwater will eliminate the need for any "slow-drip" acclimation for the fish.

 

[tetraman]

What is the maximum salinity a non-molly livebearer can live in?

 

[nmonks]

Depends. Out of the box, guppies, platies, and swordtails will take below SG 1.005 without problems. It is possible to adapt guppies (including Endlers) to full marine conditions, but this takes time. They have been used in nanoreef tanks, for example. Wrestling halfbeaks will take SG 1.005 without any problems, and possibly a little higher. Pike livebearers will easily go up to 50% seawater, and with care, even higher.

Cheers,

Neale

What is the maximum salinity a non-molly livebearer can live in?

 

[tetraman]

That's insane to picture guppies swimming around in a reef!

 

[rob newland]

Yeah neale, cfc advised me to just get a jug of high salinity water and pour it in to my puffers tank reasonably slowly - because as you say, when the tides go in and out, sg will change. I have done that with him and also my mums molly tank and have had no problems.

 

[bymauldin]

Since Bumblebee Gobies can go in either fresh or brackish would this method work with them too? I've already started cycling my tank using only freshwater. When I do my big water change at the end and add salt to the replacement water will it kill off all the bacteria I built up through cycling? Should I start my cycling process over using salt water? Or should I gradually add salt water with each replacement?