Salinity and specific gravity- goin down?!

[corinnasue]

I have a question about salinity and specific gravity. Here is my setup:

30 gallon bowfront
Inline heater. 76.5 degrees
Fluval 204
Airstone
Powerhead
Crushed coral Substrate
Red Sea Hydrometer

My hydrometer is currently reading 1.017. Goal range = 1.020

I seem to be losing salt? why? (no leaks beleive me, I checked)- topping off with only fresh water.

1. When I change water should I be replacing with saltwater at 1.020? I was told by my Fish Dealer replace only freshwater.
2. How do I safely raise the salinity? I have a choc chip star in there and I know he is sensitive to salt change. Do I pull water out of the tank, add salt and return that water?

Thanks in advance for your help. PS- this seems to be a common problem for me prior to water changes. SOS

 

[Tomd]

You should be topping with freshwater. Are topping off the exact amount? I have a line in my sump with a piece of tape?

What kind of hydrometer--They are known to be inaccurate sometimes.

2-No, you can slowly raise you SG by topping off a very little less slowly over a few days until you move up a few. Go as slowly as possible.

With no corals it is not as crucial to have salinity on the higher end, however I still recommend a refactometer to make life a little easier for you.

 

[corinnasue]

I think you are asking about my water change? Let's say I take 3 gallons out (for easy math)- i put 3 gallons back in - yes. The water I am putting back in is fresh water. Shoudl it be salt water set to the same salinity as my tank instead?

My top offs are to a predefined level on my tank, so I am not dumping in more fresh water than water that has evaporated.

2- To clarify- you are saying to let the water level drop to increase the salinity?

 

[fishfreek]

This is the logic to take with adding water to your tank.

If YOU take water out then you must put saltwater back in.

If you replace water with out having first removed it then put freshwater in.

When you remove water your removing salt and water so you must add saltwater back to replentish the salt and water you took out.

When water evaporates (you do have evaporation dont you?) the salt remains in the tank and only the water leaves so you must replace the lost water with freshwater to balance out the salt and water ratio.

If you do not have evaporation then your tank is sealed to tightly. No evaporation also means you have very poor air/water gas exchange resulting in lower oxygen levels.

 

[Tomd]

And I was talking about topoff. A piece of tape or something in the tank you use to refrence so you know how much evaporated.

It was just a guess, but that may have been how your salinity got lowered without water changes.

 

[Devilishturtles]

In a nutshell, your fish dealer told you wrong. I think fishfreek summed it up well. You should be adding saltwater in when you do a water change. Freshwater when you top off. That is the reason it is going down.

 

[Tomd]

OMG!!! I did not even read that! I was thinking topoff the whole time

 

[roka64]

I agree:
Top off with fresh water.
PWCs you will have to replace the SW you took out. If you have inhabitants, in the tank, you can raise the salinity by adding slightly higher salty PWCs.

 

[tecwzrd]

sg changes should always be done slowly (especially with sea stars) but you can also increase sg by alternatively topping off with well mixed SW one day and FW the next until you get your sg where you want it. I'd aim for an sg closer to 1.022-1.025 IMO.

SW should be mixed 24+ hours in advance before adding to the tank preferably with a power head. The newly mixed SW should match the ph/temp/sg of the main tank as closely as possible to avoid osmotic shock to your tanks stock.

Swing arm hydrometers like yours are notorious for getting out of calibration (especially if ever dropped). I'm sure your sg is lower if you have been taking out SW and replacing with FW but as already mentioned a refractometer is much more accurate/reliable.