Magnesium

[millermilla]

Hiya,

Im new to all this and am setting up a new tank. I checked my water quality before filling the tank and all was fine apart from a slight ammonia reading which seems to be OK after the salt mix has been left a while. Ive now filled the tank and added live rock and I seem to be now getting a very high Mg reading. I know most will say it's probably the test kit but before the salt mix went into the tank the reading was normal. The reading I have is an average taken from two tests. Does anyone know why the Mg is so high? What affect will this have? how can I get it down? and what is an acceptable level for Mg.

Temp: 29.5
S.G: 1.0245
PH: 8.2
Nitrate: 10
Ammonia: 0
Phosphate: 0.1
Mg: 2500ppm
Calcium: 500


Thanks

Keith

[muzzy]

hmm, i think id re-do the test or take to a lfs to test for you.
both calcium and mg are very high

mg you should be aiming for around 1350 and calcium the general opinion on here is about 400 to 420

also, temp is probably a bit high and SG a bit low, most people are aiming at 1.025 to 1.026 for sg and around 26 to 28 c for the temp.

if mg test does turn out to be correct, i guess a reasonaably big water change may resolve it

[5061litres]

acceptable for magnesium is 1300-1400.
could u do some wate rchanges to try and bring the level down?
also ur calcium is very high. do some water changes to bring them both down.
do u know ur dkh?

tony.

[millermilla]

Would the calcium being very high just be due to the 15KG of coral sand and about 30KG of ocean rock that has been added? As regards changing water which im sure will lower the Mg level I would really like to find out why it's so high in the first place? The tank was filled with RO water 5 days ago now and I know the parameters were perfect on the water when added to the tank so I dont understand why the Mg reading is so high now? I surpose im looking for the cause rather than the cure!

Thanks

Keith

[muzzy]

wouldnt have thought so, re-do the tests like said, if yopu havent added any mg suppliments i cant see how that reading can be correct

[weegaz22]

did you have the sand and rock in the tanks RO water before adding the salt? if you did then that might be whats caused the calcium to be high? as coral sand disolves at ph of 7 (which i think is what ro water is as its pure)

i may be tottaly wrong, dunno about the magnesium as i havent learnt anything about how it functions in relation to calcium and alkalinity

[millermilla]

did you have the sand and rock in the tanks RO water before adding the salt?

Good man, if thats true then your spot on ;) I filled the tank with plain RO, rocks and sand and it stood for about a day before adding the salt. Will the high calcium cause any harm though?

Thanks

Keith

[clippo]

I'd be tempted to start over.....

[weegaz22]

Originally posted by clippo@Sep 5 2005, 15:39
I'd be tempted to start over.....
why??, the calcium will come down once the tank starts to mature a bit, the coraline on the live rock will also use up the calcium as well, and with water changes the magnesium will come down (does it get used up by anything?)

i wouldnt keep anything thats sensitive to these levels in the first few weeks of a tank anyway as the levels wont be stable

[clippo]

you'll be waiting forever if you are expecting cycling/coralline algae to reduce the calcium content of the water.... best to get it right from day 1.

[lenny]

Originally posted by millermilla@Sep 5 2005, 14:09
Would the calcium being very high just be due to the 15KG of coral sand and about 30KG of ocean rock that has been added? As regards changing water which im sure will lower the Mg level I would really like to find out why it's so high in the first place? The tank was filled with RO water 5 days ago now and I know the parameters were perfect on the water when added to the tank so I dont understand why the Mg reading is so high now? I surpose im looking for the cause rather than the cure!

Thanks

Keith
i,m puzzled???? have you got live rock or ocean rock? as you say two different types in your posts. i would redo my tests if i were you very carefully as there is no way you could get that sort of reading if you put in a bucket of mg additive. you would reach presipitation way before that. also calcium should be around 420 ish but don,t worry as calcium will get used quickly. you do not state what salt, test kits ect so it,s all guess work untill you give more details. will help if poss. :cheers: lenny

[millermilla]

Hiya, the salt is Kent Sea Salt but as I said before adding to the tank it was well within parameters, there is a mix of 25KG Live Rock, 37KG ocean rock and 20KG of coral sand. The test kits are Salifert and the Mg test only goes to a maximum of 1500ppm so the figure of 2500ppm is calculated assuming 30ppm per drop of test fluid as that is the way it is calculated up to 1500ppm. After a 10 Gallon water change tonight my Ca dropped to 480 and the Mg stayed the same.

Thanks Keith

[Reef bloke]

Millermilla to be honest mate i think its the way your testing for your Magnesium.With a fresh set up there is no way your looking at 2500.Sit down and read through the destructions again mate and if need be Try testing with half the suggested tank water and reagents and divide the result by 2 and read it off the chart.
I just cant see mag being that high to be honest.

[bigbok]

don,t worry yourself over the mg or the ca concentrate on the tank cycle and the 10 pt nitrates once you have cracked that then move on to so thing more tricky you will get yourself bogged down over nothing . :thumbsup:

[lenny]

Originally posted by millermilla@Sep 5 2005, 23:17
Hiya, the salt is Kent Sea Salt but as I said before adding to the tank it was well within parameters, there is a mix of 25KG Live Rock, 37KG ocean rock and 20KG of coral sand. The test kits are Salifert and the Mg test only goes to a maximum of 1500ppm so the figure of 2500ppm is calculated assuming 30ppm per drop of test fluid as that is the way it is calculated up to 1500ppm. After a 10 Gallon water change tonight my Ca dropped to 480 and the Mg stayed the same.

Thanks Keith
hi the rock and sand will have a very small affect on your water parameters but not to the extent you are saying. as to the way you are calculating you MG you may as well guess . get a kit that you know works or take some tank water to your lfs and ask them to test it for you. not saying your stupid or anything like that but sometimes it helps to get a second oppinion. they may even know the cause if your readings are correct. i use kent salt and the readings are way off yours . it may well be you have a rouge batch of salt but then it would read high before you add it to your tank. have you checked it by mixing some in a bucket and checking that a day or so later. if that then reads high you can assume it,s the salt . just a few things to try. let us know the out come :wave: lenny
ps ... i mixed my salt water the same way you did when i set up and had no bad affects like yours. sand ect all in tank.

[~Tony~]

Hi Keith
Firstly, I would re-assess the way you are measuring Mg. I didn't think that salt water could contain 2500ppm Mg without precipitation. The Salifert kit is linear at 1500 x ml of test liquid, so if your reading is over 1500 then you can refill the syringe and continue dripping. The final reading will now be (2 - reading)x1500.
For accuracy, you should be able to drip at 0.01ml per drop or better, which is 15ppm per drop.

However, as bigbok says, I would stop worrying about your Mg & Ca and concentrate on Ammonia, Nitrite, and Nitrate. You should see these cycle and return to zero, though the nitrate may take several weeks.

Your temperature is high and I would look at bringing it down and stable. In this warm weather, consider adding a fan, preferably controlled by water temperature, blowing across the water surface to increase evaporation and hence cooling. Your SG is ok but most people intending to have corals run at the NSW reading of 35ppt salinity = 1.026 SG. For both of these parameters stability is the most important.

If you are still worried about your magnesium reading, then take a water sample to your lfs for testing.

hth
Tony

[millermilla]

Hiya,

I took all of your advise and took some steps suggested. I done a partial water change and this made little difference and was still getting very high Mg and Calcium readings so I took a sample to my LFS today who tested all parameters and only found fault with Mg and Calcium however they got results of <250 for Calcium???? and 700ppm for Magnesium and suggested I take steps to sort it out once the tank has cycled. Thinking I must have dodgy test kits I bought a new calcium and Mg Sera test kits and tested the water myself when I got home and got a calcium reading of 420 and Mg at 1560ppm. I can only draw a conclusion that either my water is so unstable it changes chemical state from one hour to the next or the spotty geek in the shop done the tests wrong and my original test kits were faulty! Ive now given up worrying about it and will just let it be for a few weeks. I was shocked when my LFS charged me £3 for the tests after I had just spent £70 on new test kits and other bits and bobs and have spent a few hundred quid in the last week or so. Maybe I expect to much! The tank is currently going a horrible brown with algae but I surpose thats as expected when new.

Thanks for all your help guys

Keith

[Reef bloke]

Water chemistry can change from day to day but not by any great deal.
The tests carried out by your lfs sound dodgy too im afraid as your set up is new i very much doubt your that low on Ca and Mg.
Your new tests give results that i would expect from a new tank set up so id go with them.
With regards to the brown algae then yes you with go from brown(diatoms) to green and blue.After you have cycled and youve gone through the algae blooms your tank should start to look a little better.

[julesandsand]

It seems to me that your latest test results are probably the most accurate.

Some lfs have no idea about customer service, you've spent all that money with them and they have the chance to greatly increase your goodwill by doing a couple of free tests and they blow it. Sounds like their tests weren't up to much either.

Best of luck.

[millermilla]

Sorry a bit off topic now but just a couple more questions.

1) I am getting brown (dusty) algae all over the tank now coupled with small air bubbles on all of the rocks, sand etc. What causes the air bubbles and is it part of the cycle?

2) I bought 25KG of live rock locally and from tank to tank the time out of water was probably only 30 minutes to 1 hour. The live rock is now in and looks great. As the live rock was from an established tank am I still likely to get a die off and will my tank still have a normal cycle as iv'e added matured rock which will act like a mature filter?

3) I always used to add activated carbon to my fish only tanks to take away the yellow colour of the water. Alot has changed in 8 years so is this still the done thing in a reef tank?

Thanks


Keith

[Kev s]

Hi Keith,

Personally I'd run the tank as it is for a couple of months keeping an eye on Amm Nitrite and nitrate, If your not going to add corals straight away then just let the tank settle down. I'm not a huge fan of lots of water changes on a new set up, I'd rather leave it unstocked and let it work itself out (as long as there isn't anything really bad going on).

No point in doing water changes if your mixed water is going to contain high readings of Mg and Ca. Have you mixed a bit of water in a bucket, left it to settle then tested it for Mg and Ca? You may have a bucket of salt where the Ca and Mg have settled out.

To help with the dusty brown algea, I'd increase water flow and reduce you lighting times.

I'd also suggest that you don't add fish for as long as you can possibly wait! I know its a pain but the longer you leave the tank uninhabited the more critter life will develop and that really helps in the long run with feeding fish like mandarins e.t.c. (I know you have that goby but I'd resist stocking straight away, it'll give you more micro life later)

Good luck with it and I'm sure you'll get it looking great after the initial set up period is over.

Kev

[Reef bloke]

The dusty brown algae is diatoms as i have mentioned above and is normal.You can still get a mini cycle when adding mature rock so i would wait at least 2-3 weeks before adding any livestock . Test for ammonia and nitrite every day so you can gauge a trend to how you tank is doing.
Slap a frozen prawn in your tank as it will get your cycle going and increase the robustness of your biological filter.

[dod]

Millermilla, just as a late afterthought, I agree with what Tony says above - I don't think that you could have a great excess of calcium, and possibly also magnesium (at least when the water is in equilibrium) as calcium concentrations are controlled by calcium carbonate solubility in surface seawater (something similar may be going on with magnesium). Also pure water, once equilibrated with the atmosphere, should have a pH around 5.6, although it would take a while to achieve this pH from comming out of the RO unit.

You could try to calculate the mass of magnesium in the tank to see how much rock (e.g. dolomite) had to be dissolved to raise the Mg level, but it would be purely academic. I'm sure you'll be fine.

Good luck, Dod