Help with my newbie Water Parameters needed!

[advocate777]

I started a new 75 gallon tank almost 8 weeks ago. It has live rock in it and some 'clean-up crew' which I got (live rock and clean up crew) from Tampa Bay Saltwater.

The test kit: Instant Ocean
Water: R0/DI
Salt mix: Instant Ocean

Okay, the tank cycled great. Ammonia levels have been O
Issue #1: the specific gravity/salinity (measured both by a refractometer and a typical fish store hydrometer)
A.) the Refractometer always reads lower than the Hydrometers (I actually use 2 hydrometers and they come out pretty close to one another)
For instance, on Dec. 23rd the Hydrometer read 1.023 and the Refractometer read 1.020
The salinity has steadily been rising.
Today, the Refractometer read 1.030 and the Hydrometer 1.30
Question: how do I bring the salinity down to acceptable range?

Issue #2
The ph today, measured for the first time since the tank was set up 8 weeks ago, measured under 7.8 because that is the lowest color on the scale.
The alkalinity, measured for the first time since the tank was set up today, measured 100 ppm or 5.6 Dkh
Question: how do I fix that?

Last issue:
I have a nice eheim water heater. But I have had some difficulty keeping the temperature consistent. In the last 8 weeks it has ranged between a low of 73 to a high of 81. There are glass covers on the tank top and the lights rest on that - gets hot....if I keep the heater on the tank gets to 78-80 range but if I turn off the heater it drops down to 73-75 range. I know we are looking to get a consistent range and not have daily drops of 78 to 73. Plus, the room the tank is in has inconsistent heat in that it is cold up here in Pennsylvania now and when the heat is cranking this room is toasty but when the heat is off it gets chilly - the room itself is hard to keep a consistent temperature in.
Question: any feedback would be great

[bnumair]

i would get a calibration solution for refractometer and use it to calibrate it. i dont have much faith in hydrometers.
salinity will not rise on its own unless ur adding something like salt or magnesium salts. or ur not topping off properly or at all. those the only ways it will go higher.
u can lower salinity by taking gal out of ur tank replacing it with straight ro/di water. also making sure u dont decrease salinity more than 1-2 points per day.
ph at 7.8 is not bad but dont need to fall any lower. u can air the air out by opening windows or installing some fans over the tank/sump.
alk is lo u can use soda ash (baked baking soda) it will also help in bringing up ph.
temp swing from 73-81 is too much of a swing if thats happening everyday. u need it consistant at 78-80 range. not sure on the heater as i dont use thhat brand.

[Chaotic Reefer4u]

+1
On Reef Doc's advise!

[StevieD]

Remove the glass covers and replace them with screen covers...I have an open top, light sits on brackets on the tank lip, and my water temp stays a consistent 80.2- 80.4...and then follow docs advice, from what Im learning and what hes said, he is spot on

[disc1]

#1 As said make sure you've calibrated that refractometer. You have to add fresh RODI into the tank to replace the evaporation. If you don't then the salinity will climb as water evaporates and leaves the salt behind.

#2 It is common for the process of cycling in a tank to drive pH and alkalinity down. It's OK until you are ready to start adding corals. Then you'll want to get calcium and alkalinity to the right place. For right now with just your clean up crew that is fine.

#3 You need some way to control the heater. Figure out how warm the room is going to make the tank on its own. Set your heater a little below that to keep the temp up if the room gets cooler. I'm not familiar with that particular heater, so I don't know how to set it or if it is even setable.

[Xadieu]

i would get a calibration solution for refractometer and use it to calibrate it. i dont have much faith in hydrometer.

No need to waste $12 to buy the solution. Use RO water and calibrate your refractometer to 0, works exact same as calibration solution at 1.026 salinity.

[bnumair]

RO for calibration is not a good idea. i know people do it i did it but is not a good idea. its best to calibrate with known salinity solution.
A refractometer measure how water bends (refracts) light. Freshwater bends light differently than saltwater so if you calibrate only using freshwater you don't know for sure it will give an exact reading when using saltwater. It should be calibrated with a saltwater solution of a known salinity...which is what calibration fluid is.

[Xadieu]

RO for calibration is not a good idea. i know people do it i did it but is not a good idea. its best to calibrate with known salinity solution.
A refractometer measure how water bends (refracts) light. Freshwater bends light differently than saltwater so if you calibrate only using freshwater you don't know for sure it will give an exact reading when using saltwater. It should be calibrated with a saltwater solution of a known salinity...which is what calibration fluid is.

I agree lights bend differently on freshwater but in my experience I have tested with RO water and calibrate it to 0 and use the solution to calibrate another fractometer to 1.026 and both gives me same result.

Unless something is wrong with my fractometer then yes i agree with buying the solution.

[bnumair]

i dont make money on calibration solutions nor i profit off my advice. I only try to help people in the right direction, direction that is 100% accurate in scientific and personal experience basis.
I am not saying its possible but i am saying its better to use calibration solution as its made for intended purpose.
Good luck and Happy reefing to OP.

[disc1]

I agree lights bend differently on freshwater but in my experience I have tested with RO water and calibrate it to 0 and use the solution to calibrate another fractometer to 1.026 and both gives me same result.

Unless something is wrong with my fractometer then yes i agree with buying the solution.

Works for some refracs and not for others. Only way to tell is to check at least once against both the solution and RO. If you can read both correctly without changing anything then go ahead and use RO but beware that it may come to bite you in the behind one day.

[Sugar Magnolia]

If you don't want to purchase calibration fluid you can easily make your own using Randy's recipe: http://reefkeeping.com/issues/2004-06/rhf/index.htm

[Spyderturbo007]

My Refractometer came with a huge sticker on the case that specifically warned against the use of RO/DI for calibration so you might want to check yours before you go that route.