[jamieb]

Hi all,

I've got a bit of a mystery on my hands. To give you some background, my tank is an 18" cube with a hang on the back refugium, after displacement its about 77 litres (20 Kg of live rock)
I have a few SPS frags which are growing well but are not quite colony's and 1 clam, again growing well but not huge.

Now, my problem is that my ALK seems to be falling very quickly, around 1 point a day (i.e 9.0 DKH to 8.0 DKH) but my calcium seems to be stable at around 430 - 440 is this a normal rate of depletion and why would the calcium stay stable?
I'm dosing Bicarbonate of soda to bring it up and to be honest theres no obvious issues with the tank it just seems like a big drop for such a small tank with a moderate amount of stock?

Regarding the stable calcium I wondered if the mineral mud and sand bed I have in the refugium is buffering this to keep the level?

Forgot to add my Mag is at 1380 but doesn't seem to be dropping quickly which leads me to believe its not a Mag issue?

Any thoughts or am I just worrying about nothing?

Thanks in advance

Jamie

[Social D]

I think you could be worrying about nothing my kh does float about a bit from 9 to 10 sometimes 11 .. I would think its the Top up water casuing this kh swing if you pour in unbuffed RO water it will have an effect on the KH and as you have asmallish tank this could be whats causing the problem, Esp if you top up every few days rather than an automated system ..

A swing of 1 isnt imo much to worry about if the tank was going from 8 to 13 all the time you would see issues with SPS quite quickly.

Calcium will be affected at a slower rate with a small tank if you have a calcium reactor or add calcium supplements.

Can you supply info on your top up regime?

[chriss]

You may find that using something like salifert buffer rather than plain bicarb does a better job. Whilst bicarb works, it's often found that it doesn't hold the alk for as long as something like salifert buffer which does a much better job.

Chris

[jamieb]

Social D, on Mar 23 2009, 12:35 AM, said:

I think you could be worrying about nothing my kh does float about a bit from 9 to 10 sometimes 11 .. I would think its the Top up water casuing this kh swing if you pour in unbuffed RO water it will have an effect on the KH and as you have asmallish tank this could be whats causing the problem, Esp if you top up every few days rather than an automated system ..

A swing of 1 isnt imo much to worry about if the tank was going from 8 to 13 all the time you would see issues with SPS quite quickly.

Calcium will be affected at a slower rate with a small tank if you have a calcium reactor or add calcium supplements.

Can you supply info on your top up regime?

I use an auto top up so its mostly spread out over the day, although it is unbuffered RO so it may be having an effect all the same.
The SPS all seem to be fine, it's just a bit odd that I'm having to add in so much a day?

Also, I was having a read up about this and over on RC they seem to advocate buffering the calcium at the same time even if it doesn't really require it? apparently to keep them in balance?
Whats the general consensus on this?

Jamie

[jamieb]

chriss, on Mar 23 2009, 08:49 AM, said:

You may find that using something like salifert buffer rather than plain bicarb does a better job. Whilst bicarb works, it's often found that it doesn't hold the alk for as long as something like salifert buffer which does a much better job.

Chris

I do have a Salifert all in one bottle which would also help with the keeping them in balance thing, do you think this would do a better job?

[Dave.I]

Just add some bicarb to your top up water.Test regularly to determin how much you need to add.If you make up a stock solution of dissolved bicarb with a set amount of ro this will give you a starting point.I run my system with the balling method and dissolve 500g of fauna marin bicarb in 5ltrs of ro and to keep my dkh at 8 to 9 i dose 260ml of this mix per day,just to give you an idea.hth

Dave

[lindsay]

As above ,bicarb will do it but i find that it does not hold the Dkh as good as a buffer unless you test a lot and buffer regularly.