cycling

[MXPX4318]

ok so here's the deal I want to set up my first brackish tank for a wonderful figure 8 puffer and I know that figs don't do to well with any ammonia or nitrites in the tank, so I was thinking I'd just get the filter ahead of time and attach it to my current well cycled and rather established (going on 5 months) freshwater tank, but then I got to thinking and remember hearing something about freshwater bacteria and saltwater bacteria being different and since brackish water has salt will that kill the freshwater bacteria?

In short will putting the filter onto my freshwater tank establish a bacteria culture that will instantly cycle my brackish tank? If so how long should I leave the filter on the freshwater tank before setting up the brackish? If not what should I do to cycle the tank (well any ideas other then fishless cycling with pure ammonia)?

Thanks in Advance
Phillip

 

[CFC]

The full transitition from FW bacteria to SW bacteria takes place at a SG of around 1.007 and between a SG of 1.000 (FW) and 1.006 there will be varying ammounts of both bacteria types present. If you place a mature FW filter onto a tank containing FW and then add the salt slowly over a matter of weeks until you reach the desired SG (in the case of F8 puffers 1.005) then you will be able to keep the culture of FW bacteria alive as well as cultivating the SW bacteria, but remember you will need a ammonia source going into the tank to keep the bacteria alive, a few mollies should do the trick or you could add pure ammonia if you are carefull with the doses.

 

[MXPX4318]

so then should I do water changes with brackish (sg of 1.005 of water added)water every monday and thursday (my normal water change days) until the sg reaches 1.005 for the tank? If I'm going to have bacteria that will denitrify (sp?) the ammonia the whole time and the F8s are coming from freshwater (which I've heard they do at fish stores a lot of the time) could I not just get the F8 and acclimize him to Brackish at the same time? because if I get mollys I won't have anywhere for them to go once I get the F8 and don't know what to do with them... well as I'm typing this I can probably just work something out with the LFS... but I'd like to just skip the molly thing if I can (by doing as stated above) and from the previous post how long will it take to develop a bacteria culture in the filter that I want to use?

 

[CFC]

The trouble with adding the puffer and then raising the salinity is that puffers dont take well to unstable water parameters and mat become stressed, it would be easier on the puffer to just be drip acclimatised to the brackish water once rather than have the water chemistry change suddenly once or twice a week. Mollies are some of the hardiest fish going so these make a good first fish for brackish tanks.