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-   -   SG Question (http://www.aquariumadvice.com/forums/f11/sg-question-84564.html)

Viperboy 10-04-2006 01:14 AM

SG Question
 
Ok so my hydrometer is reading 1.028 for my tank which seems a little high and when i tested my tap water it read 1.001 so im guessing the actual SG of my tank is around 1.027 which is still .002 higher than i would like it because i want around 1.025 for my reef and fish .... my question is can i just add tap water to my tank to get it back to where it needs to be but doing this slowly over a period of time .... and the other question i have is does SG go up as water get evaporated from the tank? ... TIA

Ray

sir_dudeguy 10-04-2006 01:27 AM

first i'd get a refractometer...much more acurate than a hydrometer.

But yes, the sg does go up when water evaporates. When water evaps, its just pure water with no salt in it...so the salt stays behind. What happens when you keep the same amount of salt, but less water? yep, there's a higher salt concentration, so your sg will be higher. So are you topping off with freshwater?

Viperboy 10-04-2006 01:36 AM

nope have never toped off with freshwater ... should i be doing this? ..... how often? .... and i cant afford a refractometer right now or i would

Ray

Finatic 10-04-2006 01:54 AM

Try here http://search.ebay.com/_W0QQfgtpZ1QQ...QsassZgreatdel

for a cheap (about $20 depending on auction) refractometer. I just won mine and am waiting for delivery, so I can comment on quality when I get it.

sir_dudeguy 10-04-2006 01:54 AM

yes, you should be topping off with freshwater, and doing that daily. If you find that a problem, then i suggest an auto topoff unit, tho imo they're not needed. Some will say "well i need one because i'm always at work and dont have time to top it off..."
So when do they feed the fish? How bout water changes? imo topoffs are over rated and i see no reason why you cant just top off with a jug of water whenever needed. Now i'm not bashin on you in any way at all, so dont take it like that. I'm just saying that people in general make topoffs a bigger deal than they should, so just dont let that get to you..

enough rant tho lol..basically just make sure that you top off whenever you see that it's low, which for me is once a day, sometimes 2.

Do you have a glass lid on your tank by any chance? Just wondering cuz you say that you've never had to top off before....

hth :)

Viperboy 10-04-2006 02:00 AM

Well i never knew i had to do this and was never told when i started out .... so when my water starts to get low is when i usually do a PWC and it gets full again ... but i guess that explains why my SG has slowly been rising and its not a big deal at all for me to top off at least once a day with a pitcher of water or something so u didnt offend me at all .... also i do not have a glass lid on my tank i actually have an eggcrate i cut to fit the top perfectly

Ray

theatrus 10-04-2006 02:02 AM

I run an autotopoff, probably the best thing I did (especially since it now runs through my kalk reactor). Having that water container of 30some gallons of RO water ready to go in emergencies is also great.

But yes, you need to topoff water lost in your tank with freshwater. If its straight from the tap, do whatever you do to get rid of the chlorine first.

Viperboy 10-04-2006 02:14 AM

Ok well i just got some tap water and put my prime in it and topped off my tank this second so we will see if the SG goes down just a bit ... but then when i do my PWC ill have to add a bit lower SG water to get it back down to 1.025 which is where i want it ... but thanks guys for this information im suprised that with all the reading i have down and having my tank up and running good for 3 months that i have not heard of this ... but thank you and i will make sure to check it daily

Ray

melosu58 10-04-2006 09:40 AM

We learn something every day. And you learned something very important today.

roka64 10-04-2006 10:33 AM

Quote:

Originally Posted by melosu58
We learn something every day. And you learned something very important today.

I agree!

Viperboy 10-04-2006 11:57 AM

You can say that again

sir_dudeguy 10-04-2006 01:14 PM

ya no top offs, combined with doing water changes and topping off then is whats made your sg go up. I'd just take out a bit of water and add freshwater...let it be for a while, then if its still too high, do it again.

But i'd suggest using RO water, and not using tap. Tap water will have nitrates and phosphates in it more often than not, and the water conditioners dont do anything for that. Since you dont have an RO unit, i'd just go to either a water store like watermart, water and ice, or go to your lfs (they usually have it) or even walmart and get RO water. Tap is often the cause for algae cuz of the nitrates and phosphates.

melosu58 10-04-2006 01:23 PM

Quote:

Originally Posted by sir_dudeguy
Tap is often the cause for algae cuz of the nitrates and phosphates.

:thumb:

jgallo 10-05-2006 02:30 PM

I have a 30 gallon sump--- that acts as an auto-top off right? then I just add fresh water to the sump every few days, when the water is lower in the sump??

roka64 10-05-2006 02:37 PM

Quote:

Originally Posted by jgallo
I have a 30 gallon sump--- that acts as an auto-top off right? then I just add fresh water to the sump every few days, when the water is lower in the sump??

I would say, yes. I don't have a sump, but I have my tank marked with tape, when the water level goes below that, I add tap.

Sparkie 10-05-2006 02:42 PM

Jgallo, even with a sump you will need to topoff your water every day. It still has "tank" water in it which will effect your sg. I have to add water every day. Usually about 1/2 gallon. If I dont I see a spike in my sg.

sir_dudeguy 10-05-2006 04:20 PM

Quote:

I have a 30 gallon sump--- that acts as an auto-top off right? then I just add fresh water to the sump every few days, when the water is lower in the sump??
no, it is NOT a top off unit. No you wont see the evaporation in the main tank, but you will see it in the sump. What i do is draw a line on my sump for where its sposed to be. Every day i fill it up to that line 2 times...i only let it get down like a half inch or so before i top off tho. So i get about a gallon a day in there.

But its still tank water running thru the sump, so when the water evaps from there, its gonna affect the water thats in the main tank, because its the same water.

But yes, that would be the place to top off at (in the sump i mean). Its easier to just dump in water in there than it is to just dump water in the main tank, mainly because when you do it in the main tank you kick up a lot of sand, blow the corals around (or knock them off), etc...in the sump, i just do it on the return pump side and its just glass in there..no problems

roka64 10-05-2006 04:36 PM

Sorry, I didn't mena to quote the whole thig. I meant:
I just add fresh water to the sump every few days
Yes, sorry about the confusion.

10-05-2006 05:58 PM

Everybody has given good advice. It is a good thing nothing went wrong by the SG flucuating that much.

Just thought I would mention that my hydrometer is off a good amount. The only thing I like it for is mixing new salt because I know where it is suppose to be compared to my refrac.

sir_dudeguy 10-06-2006 12:50 AM

ya hydrometers are usually off it seems...so in the future i suggest buying a refracto


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