Salinity test for freshwater tanks?

MalcolmV8

MalcolmV8

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May 31, 2003
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I've searched high and low and can't find a refractometer or salinity test for freshwater tanks. Are they out there? any links?

When you google it all you find are a bunch of replies about not needing to test it, just do water changes and add your 1 tablespoon per 5 gallons and it'll eventually be right blah blah. yeah I know all that. I'd like to actually test it though and see what it is. I often wonder where mine is at and would like the ability to test it.
For example I have multiple tanks at home and often wonder why I have variations between them. Sometimes certain fish or snails or even plants with thrive in all but one of my tanks and when looking for differences and issues salinity of the water is one thing I'm always guessing.

Also who's to say how accurate or rather inaccurate my water calculations are each week when I do water changes and slowly over time I could have some tanks much saltier than others.

Anyhow I was wondering if anyone found something that will work that's reasonably priced?

Thanks
Malcolm
 

MalcolmV8

MalcolmV8

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May 31, 2003
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Since google can answer that question better than me here's a quote

Freshwater fish are saltier than the water they live in.
About 50% of the exposed surface of a fish is permeable to small particles. This is why water quality is crucial to the well-being of a fish. Typically, the bodily fluid of fish contains more minerals and ions than the surrounding water. As a result, there is constant influx of water into the fish through osmosis, diluting its body fluid. In order to maintain their salinity level, fish are constantly excreting urine. At the same time, they absorb salt from the water via special cells in their gills. The constant exchange of minerals and water is crucial for survival of the fish.
Click to expand...
 

MalcolmV8

MalcolmV8

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May 31, 2003
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Well if you go google for adding salt water to fresh water tanks you'll find tons and tons of info that lists the benefits and the info like I posted above. There's also sites that say don't bother with it. There's no definitive answer when searching online as to what's best. I too have had tanks for many years and I've done both with and without salt.

Anyhow I just wanted to know if anyone can tell me where to find a freshwater salinity meter that doesn't cost $200.
 

aakaakaak

aakaakaak

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#6
Sep 9, 2010
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Malcolm,

Certain fish will die in your tanks if you add marine salt. A small amount of aquarium salt will be okay, but adding too much will likewise be hazardous to any fish without scales.

The larger a molly gets the more they like brackish water. That's about the only thing you would have to worry about. All your other fish have swim bladders set up for freshwater. You could potentially cause a bout of artificial swim bladder disease if you're not careful with the salt.

That being said, you're looking for a Hydrometer that measures gravity:
Hydrometer - Saltwater - Fish - PetSmart
You should find them close to the bags of Instant Ocean Marine Salt or other saltwater related products. It works for both FW and SW normally. The gravities are just different.
 

O

OrangeCones

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Feb 27, 2009
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I've only added minerals when using straight RO water (not aquarium salt, but a complete mineral replacement). I used a TDS meter that came with my RO system. It doesn't measure salinity, but ALL dissolved solids suspended in the water sample. I breed soft water fish and live with hard tap water, so I usually just mix RO with tap to get the right mix.

I've never used aquarium salt except as an emergency aid to prevent nitrite poisoning when I lost power to my house for 4 days after a hurricane and lost most of my beneficial bacteria due to lack of oxygen. I keep it on hand incase I need it, but don't use it normaly. I don't think it hurts, but I've never had health issues in the fish, so don't think its essential.

Just my 2cents.
OC
 

MalcolmV8

MalcolmV8

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May 31, 2003
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aakaakaak said:
Certain fish will die in your tanks if you add marine salt.
Click to expand...
Correct. I don't use marine salt though, just normal freshwater aquarium salt you get at your local pet store.

aakaakaak said:
That being said, you're looking for a Hydrometer that measures gravity:
Hydrometer - Saltwater - Fish - PetSmart
You should find them close to the bags of Instant Ocean Marine Salt or other saltwater related products. It works for both FW and SW normally. The gravities are just different.
Click to expand...
Actually Hydrometers are not very accurate even for salt water tanks. You'll see most salt water guys switch to refractometers which measure the refraction of light through a water sample to determine salinity level. However even those are not calibrated low enough for freshwater aquariums.
 

MalcolmV8

MalcolmV8

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May 31, 2003
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Orangecones, I've been using normal tap water for many years but I've recently setup an RO/DI filtration system in my basement and in the next few weeks when it's completed and ready I'll probably switch my freshwater tanks to ro/di water.
I've also considered stopping salt to see what affect it has on my plants. All my tanks are live planted and I read online a lot that salt is no good for plants at all. Mine seem to do OK but I wonder if they'd do a lot better without the salt.
 

nanu156

nanu156

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Mar 8, 2010
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Well first, Salt kills snails, and plecos... SOOOOOO... stop using it or re-home those friends.

I won't even use it for ich with out removing my plecos... but up to you.

No salt for plecos, loaches, catfish, or inverts. (snails shrimp)
 

MalcolmV8

MalcolmV8

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May 31, 2003
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nanu156 said:
Well first, Salt kills snails, and plecos... SOOOOOO... stop using it or re-home those friends.

No salt for plecos, loaches, catfish, or inverts. (snails shrimp)
Click to expand...
Humm I must have very little salt then because I've had my pleco for ahh 4 + years now and he's growing awesome. I've had him since he was just a tiny little squirt. Catfish I've had a long time too. They're more than double the size when I got them. Heck even my loache has been around for a few years.
Well I could certainly stop using it. I'm not hell bent on using it or anything like that.
 

aakaakaak

aakaakaak

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Sep 9, 2010
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#12
The best you're probably going to get for FW are probably Hydros then. Yeah, they're not super accurate, but they're better than nothing.

Careful with your plants. Some are fine in up to brackish water. Others will melt in less than brackish. The extra salinity can change their water absortion from suck to blow, effectively dehydrating your plants to death. It all depends on the plants.

Which kind of mollies do you have anyway? Are they the gigantic mexican sailfins or the little 2-3 inch buggers? (The bigger they are the more brackish they like.)
 

MalcolmV8

MalcolmV8

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May 31, 2003
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In my 90 gallon I have the 2 - 3 inch kind. I also have one of those really odd looking ones. It has a huge belly and a funny shape. I think they're called sale fin mollies but I forget? Anyhow the sale fin is in the 20 gallon where it behaves. In the 90 gallon for what ever reason it will not stop chasing everyone and causes to much stress to everyone else.
 

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