Low Alk., High Mg in a Cycling Tank

[eniram]

I'm just starting out on marine tanks, so please excuse any mistakes or misunderstandings I make.

I am five weeks into cycling a 120 litre tank with about 35% live rock. Everything appeared to be going normally until about a two weeks ago.

The ammonia and nitrate spikes came and went in the first two weeks. I have been doing a 10% water change weekly, using RO make-up water and Red Sea salt. I have been adding the recommended bacteria. Temperature has been stable at around 25- 26 throughout and the S.G has always been 1.020 to 1.024. Ammonia, Nitrates and Phosphates are now all within limits. I have a lovely dark green carpet of algea on the sunlit surfaces of the LR.

Then two weeks ago the calcium dropped below 370, the pH went above 9.0 and over several days, the Alkalinity went down to 1.1. (I have checked it with a comparitor and a photometer so I am sure it is correct)

I added calcium and now have that back around 400. I have slowly been adding Red Sea Buff for the Alkalinity and it is slowly rising, but is still at just 1.4. The pH is coming back down and last night was at 8.4.

I have only just today received my Magnesium titration kit and is is off the scale at >1280ppm (titrated twice to check)

Can anyone help with some some advise please on how to now get the Mg down without effecting the S.G. and do I still continue to slowly add Buff to get the Alk up?

And on a different note - I am new to this web site and I must say there are some very impressive marine reefs on display - I admire your work.

And for anyone wanting to know what eniram stands for - I'm not that creative with Nicknames so I just spelt Marine backwards - all I could think of!

[wasp]

Your magnesium is where it should be, somewhere around 1250 to 1400 is fine.

Calcium at 370 is nothing to panic about, but if you want to maintain it at 400, adding some calcium is the right thing to do.

Something funny about your alkalinity though. Are you talking Mg/L or DKH? Either case the numbers you mention seem unlikely especially as you had a high pH. If you know any other reefers you should ask him to test a sample of your water to double check the accuracy of your kit, or if you don't know anyone yet, take a sample of your water to your local marine fish shop and ask them to test the alkalinity for you. Once you have established the correct alkalinity then post it here and we can advise what to do next.

BTW, if you don't yet have any livestock in the tank, it will not matter much what your calcium and alkalinity are at this stage.

[eniram]

Wasp,

Thanks for the prompt response and the "heads up" that Mg and Ca are okay where they are (were).

I am reasonably confident the Alkalinty (DKH) is correct. I am using both a reagent/comparator and a photometer to check it and they have verified against each other from the beginning. Alkalinity was around 2.3 - 2.5 DKH from the start and then started dropping when the pH started to climb (and my limited knowledge of chemistry suggested that if Ca & Alk. were dropping, why was the pH rising?) I am also sure I have the pH rise recorded correctly as I checked that using two reagents kits and the photometer!.

Anyway, I will take your advice and get a sample analysed for Alk. at a Marine Shop and advise. Thanks

[davidb]

do that... i cant see why your Alk could be so low and your pH high either- with such a low alk your pH should be about 7.5!!!!

[reef]

i would not worry about mag/cal/alh in a cycling tank.

Wait until stock is to be added then test.

Dont add anything until tank is fully cycled. no need to get the levels correct as once the tank is cycled do a 50% water change and the levels should balance out.

best to aim for calcium levels of say 380-420ppm. alk of say 2.5-3.

But only after the tank has matured.

So at this stage just leave the tank and just take your time and let it settle in.

i would run the lights say 2-3 hours a day otherwise you might get bad algae.

[dogmatix]

I would say that because your levels (no2,no3,nh4) i starting to drop back down to zero that it why your Ph has stabilized and started t climb. Your system maybe starting to use the carbonates for coralline algae growth. As wasp said your levels are fine, and like reef said just do a good water change to bring it back up.

I would also say that your test for alk was in Meq's as DKH test kits do not measure in .3's and .5's , but rather in whole numbers. If your test is in meq's again those readings are normall.

HTH

Ben

[chimera]

hehe, marine backwards,... nice

[davidb]

wow how did you notice that chim? you must be good at wordfinds

[Chazza404]

...... or eniram said it at the end of his first post above ^^

[eniram]

Hey thanks Guys - all good advice from Davidb, Reef, Dogmatix.

Okay, first thing - I've had the lights on too long per day - was at twelve - will slowly pull that back. Perhaps that's why I had a wee burst of some pretty ugly looking green strand like algea - looked a bit like didymo!! I brushed it all off, it disappeared into the filter and hasn't come back (yet!)

Tested again tonight and pH is 8.4 and Alk 1.45 (and yes Dogmatix, it is meq/l not DHK as I thought - Duh! But I will take the advice not to worry too much about it and wait to the cycling ends and do a 50% change and see what happens then.

And just exactly how do I tell when the tank is fully cycled please Guys?

[wasp]

Once the ammonia and nitrite are at zero, the tank is considered cycled. There will still be nitrate, but this is less toxic and you can start slowly stocking the tank. The nitrate eating bacteria take several months to really kick in.

Your alkalinity is still too low for good health of some organisms, in Mg/l it should be at least 2.5. I am not sure what Red Sea Buff actually is, long as it's carbonate alkalinity rather than borate alkalinity it will be fine (assuming you plan to keep corals). Once the jar runs out though, use baking soda. Much cheaper, and does a good job.

I still think you should get your LFS to check your alkalinity with a different test kit.

[lduncan]

Your alkalinity is still too low for good health of some organisms, in Mg/l it should be at least 2.5. I am not sure what Red Sea Buff actually is, long as it's carbonate alkalinity rather than borate alkalinity it will be fine (assuming you plan to keep corals). Once the jar runs out though, use baking soda. Much cheaper, and does a good job.

I agree, just use baking soda. Red Sea buffer, is essentially just a mix of baking soda, and washing soda. So it's all carbonate alk. (Seachem seem to be the main offenders in boosting borate alkalinity, which is not detected by most test kits)

I still think you should get your LFS to check your alkalinity with a different test kit.

Yeah, double check that alk reading with another test kit. Seems to be very low. What brand test kit are you using now? Sure bacteria can be fairly large consumers of alk, but with nothing else in the tank, I doubt they have used it at a rate to bring the alk down that much.

Also are you using NSW or ASW? What's your salinity at?

Layton

[wasp]

Also are you using NSW or ASW? What's your salinity at?

Layton

I have been doing a 10% water change weekly, using RO make-up water and Red Sea salt. I have been adding the recommended bacteria. Temperature has been stable at around 25- 26 throughout and the S.G has always been 1.020 to 1.024.

[lduncan]

Maybe I shouldn't have skim read it

[eniram]

Oh you Guys know your stuff don't you?

Purchased a titration Alkanlinity Testing Kit and here are the results:

Comparitor Test 1.5 meq/l

Photometer Test 1.59 meq/l

Titration Test 2.6 meq/l

So my comaparitor test kit is definitely "stuffed" and I my photometer is actually designed to test potable (fresh) water, so perhaps it throws a "wobbly" when given saltwalter - maybe?

Thanks for all your help and advice - I am now back on track thanks to you all.

[wasp]

[davidb]

from me too