Turning My Water Brackish?

[Doug62]

I currently have a 100 litre tank with Mollies and guppies in. I want to turn the water brackish and have bought some marine salt (instant Ocean? i assumed this is the right stuff). Anyway, what i'm unsure of is how much water i should mix the salt with, prior to adding it to the tank? I assume i can do this in one go provided i use enough water to mix it with.
Cheers
Doug

 

[nmonks]

CFC covers the basics in the pinned topic at the top of the forum. My Brackish FAQ covers these topics in much more detail.

The key thing is not to increase the salinity too quickly. The mollies won't care, but the filter bacteria will. I'd take the salinity up to around 1.005 within a week or so, by making a series of water changes, and see how the nitrites look. If everything is still okay, nudge yourself up by one "number" on the SG scale, e.g., 1.005 to 1.006, with each water change. At some point, your freshwater filter bacteria will be replaced with marine ones (or perhaps adapt) but in between you can get something a lot like new tank syndrome. So go slowly. That said, I've gone from fresh to brackish many times, and never had any serious problems.

Guppies aren't really brackish water fish, even though they can adapt to even fully marine conditions. They're so inbred now that it's difficult to predict how they will react. Endler guppies at least seem to be pretty tolerant of brackish water. All your mollies are fine though, and will be fine at even 1.010, and many do well in marine conditions, too.

Cheers,

Neale

 

[Doug62]

Thanks neale,

Can you recomend a particular hydrometer?

Cheers
Doug

 

[AMS]

Most floating style hydrometers dont measure waters with a specific gravity under 1.010, so your looking at a swing arm style hydrometer or even better a refractometer.

 

[Opcn]

I'd recomend skipping the hydrometer and going straight to refractometer http/www.drsfostersmith.com/Product/Prod...7&N=2004+113761 43 plus shipping, for peace of mind, worth it in my opinion.

 

[nmonks]

Refractometers are great, but, and I've said this before, they're overkill for brackish water fish and invertebrates. If you want one, then go ahead and buy one, but don't convince yourself you need to because of the brackish aquarium.

All brackish water fish, all of them, are adapted to changes in salinity. Adult scats can be taken from freshwater and dumped in seawater with no ill effect, supposedly (never done this myself). Certainly mollies can be adapted between fresh and seawater in about an hour or two.

There's no reason a brackish water tank needs an exact salinity, and in fact it is better to vary the salinity with each water change. Far more natural. In many cases, species will be encourage to spawn if you do this (examples include garpike, glassfish, and monos). It is simply a waste of time and effort to try and keep a "steady 1.010" in a brackish tank; these fish live in varying habitats and couldn't care less if the salinity is 1.008 before a water change and 1.012 afterwards.

Me? I use a cheapo floating hydrometer. Cost about 4 UK pounds, or about 6 US dollars. Even if it's off by 10 or 20% compared with a refractometer, that's plenty good enough for brackish.

Cheers,

Neale

 

[AMS]

I personally use a refractometer myself, in my brackish tanks and in my reef. Like nmonks says its more natural to slightly alter the salinity with each water change. I do alter the SG with every water change myself, but I like to know the exact SG in which I am adding to the tank. Refractometers are quite useful if they are used in planted brackish tanks as well.

I only spent $50 on a new refractometer, IMHO its a small price to pay especially for planted brackish tanks.

 

[Doug62]

Thanks all,

I think i'll be going with neales advice on this one, particularly as i'm at university and finances are tight-ish. Anyway, he seems to be the dogs-bollocks when it comes to brackish so that'll do me. I do have lots of plants in my aquarium (some of which came with the tank and have comprehensive root systems and have sprouted fresh plants all over the tank!!) and i'd really like to keep them if possible. Therefore, i was thinking of have my water at about 1.003 to keep the conditions mildly brackish. Would this be suitable for the Mollies? I think i've read this is the minimum somewhere.

Cheers
Doug

 

[AMS]

1.003 is fine for mollies. There really is no minimum really, mollies can live in hard alkaline freshwater right up to marine. What plant species do you have at the moment? Also what fish other than guppies and mollies?

 

[Doug62]

No other types of fish, so i'm going to wait until the tank is settled in as brackish before i add other suitable fish. I'd love a puffer but i have read theyre too aggressive for peaceful livebearers. As for the plants - one is 'Hygrophila corymbosa', i'm pretty sure another is fanwart (possibly carolina) but i cant locate the rooted one - any link to a plant identification site?

It has long stems with long skinny leaves on the end is the only way to describe it

 

[nmonks]

Pretty well any plant tolerant of hard water will be fine at SG 1.003. It's around the 1.005 mark that you need species particularly adapted to brackish water, like Cryptocoryne ciliata and Crinum calamistratum. If you're using a hydrometer, it's important not to add too much salt if you've got plants, so err on the side of caution. One other thing. Hydrometers are calibrate to a certain temperature, so if you mix the salt with cold tap water, the reading will be wrong. Let the water at least get to room temperature, ideally aquarium temperature. Adding from the hot water tap is questionable because of copper contamination from having the water sitting in the tank. It should be fine, but some people caution against it.

Cheers,

Neale

 

[Doug62]

Thanks for the heads-up ,
As i will be adding my salt by way of water changes then i will bring it up to aquarium temperature from cold anyway. Do you think that a general salinity of 1.003 is enough tho? I want my mollies to be happy but i dont want to risk the guppies that are in there if i can help it! Thats why i thought a mild brackish might work. Also, the water in my area is very hard so this should bode well for the plants.

Thanks
Doug

 

[nmonks]

1.003 is fine. The mollies will thrive, and the guppies won't care.

Cheers,

Neale