Trying To Get Sg Right-help!

[BecciMac1987]

Sorry if this sounds confusing, I will try and make it as clear as poss!
I have a 100l brackish tank that I want around 0.013sg (GSP & Shark catfish so must be quite strong)
I know I can use marine salt, but have been using 'Aqua Tonic Salt' by Interpet as its cheaper.
The aqua tonic salt says use 1 tablespoon per 5 gallons for a brackish tank of 0.1% Huh? I used my hydrometer (cheap glass floaty thing) and it reads at 0.001 (basically miles from where I want it).
So..... do I add more tonic salt or just buy marine salt? How do I measure either?
Ahhh Im all confused

 

[nmonks]

You don't need SG 1.013 for GSPs and ariid catfish; SG 1.010 is ample, and even slightly less (say, SG 1.008) would be acceptable provided pH (7.5-8) and hardness (15+ dH) were maintained appropriately.

Aqua-tonic salt isn't an option; you need to use marine salt mix. If using a lower salinity allows you to reduce your consumption of marine salt mix, so be it. But only marine salt mix contains the carbonate salts and other minerals essential for raising the pH and buffering against pH changes.

SG 1.010 is about 15.5 grammes per litre at 25 C. You can use my Brack Calc program to quickly figure out the amount of salt for any salinity. Tablespoons per gallon is a daft way to go about this problem! Just grab some kitchen scales and weigh out the salt. Add to the bucket and stir well. Test the salinity, and adjust with more water or salt as required.

Cheers, Neale

 

[BecciMac1987]

Ok thanks, I was using the tonic salts cuz the packet says for brackish aquaria-very misleading then.
I only thought I needed a high sg cuz of the shark which I was told needs almost full marine when mature-is this not correct either?
Thanks x

 

[nmonks]

Tonic salt is often added to livebearer tanks, and decades ago was sometimes used for brackish water fish like gobies. While it won't harm brackish water fish, it is very expensive to use in the quantities required, and isn't all that effective either. As I say, better to use slightly less marine salt mix if you need to stretch your pennies (and who doesn't these days).

There's no "golden salinity" for most brackish water fish. Shark catfish certainly shouldn't be kept in freshwater conditions indefinitely, but once the water is at least somewhat brackish (SG 1.005+) they aren't that fussy. Wild fish swim in and out estuaries all their lives, and are what ichthyologists call "euryhaline", i.e., they can adapt to most any salinity between freshwater and marine conditions. What they care about more is that the water should be clean and the filter strong: these are migratory fish, and they LOVE to swim into strong currents.

Do also take care to have at least two, and preferably 3+ specimens. These are incredibly gregarious catfish, and get very lonely on their own, usually becoming shy and nervous. Aquarium specimens get to about 20-25 cm, so they're biggish fish to be sure, but despite being (literally) armed to the teeth, they are real "pussy cats" that will appreciate every bit of love you give them.

Superb catfish, by the way. In my opinion the most shark-like fish in the hobby, and wonderfully hardy and peaceful as well!

Cheers, Neale