refractometer/hydrometer dilema

[metree7]

I decided to purchase a refractometer because of the positive things I have heard about them on this site. I have been using a hydrometer for the past month and only started using a refractometer for the past week or so. My refractometer compensates for temperature and I calibrated it with distilled water. I have been using both the hydrometer and refracto in order to check my salinity in order to have a checks and balances system. Instead, my hydrometer( which I have used for a month, and I have fish, and other critters), reads 1.022, and my refracto reads at 1.025. I dont understand why there is such a difference and I dont know which instrument I should trust. everyone says that refractometers are very accurate and reliable, but I find myself trusting the 15 dollar plastic hydrometer, because I have been using it for a longer time and my fish seem to be doing well. The thing is, if I use the 1.025 reading, then I have to put fresh water in the tank in order to drop it down to 1.022. But if I do that and the salinity is really 1.022 to begin with, then I will end up with water which has less salt than needed. Any tips, trick, suggestions?

 

[Fishguy2727]

Trust the refractometer. Your fish are doing fine in either salinity, it is corals that will show the difference. Fish will be fine from 1.018 up to 1.028, 1.028 being natural seawater. One of the LFSs around here actually keeps their fish at 1.013 and they do very well (until their customers put them in their 1.025 reef tanks). Fish tend to do better at lower salinities than natural seawater. If you are not doing any corals or invertebrates and want the specific gravity at 1.022 go by the refrac.

 

[Kurt_Nelson]

Yup... trust the refractometer. However, I'm not sure why you need to add freshwater to lower your salinity. You say yourself everything is doing just fine, so why not just leave things the way they are? Regardless of whether you're at 1.025 (which you most likely are) or 1.022, your tank is happy. A healthy/happy tank is more important than a tank at 1.0xx salinity - whatever that number may be.

 

[metree7]

Fishguy, that is some great information on the various salinity levels and the animals that can live within those ranges.
Kurt, although my fish have been doing great in the saltwater that I have prepared for them, I have been trying to lower my SG to 1.022. The reason being is that my Saltwater Aquarium Book, says that fish only with live rock setups,( wich is the one that I have) have a range of 1.022 to 1.024. And that reef setups start at 1.025. Either way, like you mentioned my fish are doing great and maybe I should just concentrate on keeping a stable SG reading. although, wouldnt it save me some money on salt if I lowered the SG, in the long run?

 

[Fishguy2727]

It has been shown that fish do better at lower salinities, 1.019 or so being ideal. However, at this salinity you could lose many of the beneficial invertebrates that live rock is all about. It can also screw things up if you choose to go reef later (the lower salinity and/or the lack of inverts).

What size tank?
What fish?

 

[Kurt_Nelson]

...The reason being is that my Saltwater Aquarium Book, says that fish only with live rock setups,( wich is the one that I have) have a range of 1.022 to 1.024. And that reef setups start at 1.025.
...

I think the missing key word there is "... *can* have a range of 1.022 to 1.024. " There is nothing that says they *should* have a range of that. The ocean is, on average, about 1.026. Reef or not, fish are used to that level.

I'm not arguing the fact that fish may do a little better at somewhat lower salinities - just saying that sometimes if it ain't broke, no need to fix it.

Regarding $$ savings on salt with the lower salinity... yes, you would be using a little less salt. But I can't imagine it would add up to much in the long run when you consider all the other costs of keeping a sw tank.

 

[ccCapt]

It has been shown that fish do better at lower salinities, 1.019 or so being ideal. However, at this salinity you could lose many of the beneficial invertebrates that live rock is all about. It can also screw things up if you choose to go reef later (the lower salinity and/or the lack of inverts).

What size tank?
What fish?

Can you show any studies that say that?
You may want to do some further research.
Ron Shimek's Website...Critters
"The bottom line for salinities is simple. There is simply no reason at all to maintain the salinities of our systems below normal reef conditions. All reef inhabitants will suffer damage from prolonged exposure to lowered salinities. Invertebrates kept at low salinities often die within a few days to a few months. Given that corals, sea anemones, sponges and some other invertebrates have no old age or senescence (or to put it another way, they are immortal), low salinities result in a quick death. Some mollusks, crustaceans, and most fish kept at low salinities die of kidney failure; it just takes them longer. A fish which dies in a couple of years in a hyposaline aquarium may have had the potential to live more than 20 years had the salinity been appropriate."

 

[melosu58]

I totally agree. You`ll want to keep it where nature has it set. 1.026 is the ideal setting. I would keep it as close to that as possible.