Donate to the running of ReefBase

We don't display ads, and we don't charge suppliers. This allows free, unbiased speech and opinion. Any donation of any amount really helps with the running costs.

Donate £1.00 Donate £2.50 Donate £5.00 Donate £10.00 Donate £20.00 Donate another value

Calcium levels

0 Members and 1 Guest are viewing this topic. 372 views

  • Posts: 16
  • Liked: 1
  • Thanks Given: 1
  • Received: 0
  • Location: Clacton-on-Sea

Hi guys, sorry if this isn’t the right place to post but I’ve been checking my calcium levels and they’re about 350ppm which is low, I have down a couple big water changes and still reading the same, without dosing what’s the best way to bring it up?

Many thanks


  • Posts: 139
  • Liked: 12
  • Thanks Given: 8
  • Received: 21
  • Location: south west

Reply #1

Magnesium Chloride Hexahydrate Flake


  • Andy
  • Global Moderator
  • Posts: 973
  • Liked: 254
  • Thanks Given: 171
  • Received: 179
  • Problems: 99
  • Tank Thread:'-tanks-6/andy's-85l-nano/new/#new

Reply #2

First thing to do is get another calcium test kit and double check,  they do go off.

One way to increase it is to use a salt mix with raised elements, e.g. Red Sea Coral Pro (black bucket), however that will also affect your alkalinity etc too.

I know you said you don't want to dose but it really is pretty easy even without a dosing pump.
 Just get some Red Sea foundation A liquid and follow the dose instructions.  You don't need a doser, it really is simple.  1ml increases 100L by 2ppm, so you just multiply that by the size of your tank.  Increase it by say 30ppm a day until you reach your target then just dose a small amount by hand each week to keep it stable.

If it's a big tank, then buy the powder version and mix up some stock solutions, works out a lot cheaper.


  • Tim
  • Global Moderator
  • Posts: 2,657
  • Liked: 701
  • Thanks Given: 359
  • Received: 587
  • Location: Camberley
  • Tank Thread:'-tanks-6/tims-first-and-last-upgrade/msg42396/#msg42396

Reply #3

Low magnesium can stop you raising calcium, what is your magnesium level?

Best way is to dose a premixed calcium chloride or get the powder if it’s a larger tank as has already been said.



  • Posts: 16
  • Liked: 1
  • Thanks Given: 1
  • Received: 0
  • Location: Clacton-on-Sea

Reply #4

Hi guys

Thanks for your responses I’ll have a further look into it, I don’t mind dosing I just don’t understand it enough at the moment.. I’m learning it all slowly but surely LOL. I’ll look into the foundation A, I have a 350L system so would what would you recommend, powder or liquid

Many thanks


  • Global Moderator
  • Posts: 1,699
  • Liked: 513
  • Thanks Given: 70
  • Received: 320
  • Tank Thread:'-tanks-6/fr499y's-4-footer-mixed-reef/

Reply #5

powder, cheaper in the long run. Can mix it up to how you want it for a start :)


  • Posts: 16
  • Liked: 1
  • Thanks Given: 1
  • Received: 0
  • Location: Clacton-on-Sea

Reply #6

Hi guys just quickly, I have bought some reef foundation A I’m a little confused on the measurements etc (I’m not very mathematical LOL) I have a 350L tank also might sound a silly question but do you add it straight to the display tank or through the sump?

Many thanks again


  • Posts: 341
  • Liked: 98
  • Thanks Given: 23
  • Received: 47
  • Location: Kent

Reply #7

This calculation only works if you account for water displacement by rockwork and equipment. Most 350L tanks won’t have 350L of water in them. If you don’t know your actual water volume go conservative on the dose.

1ml (if you have the liquid) brings 100L of water up 2ppm. As you tank is 350L, 1.75ml will bring it up 1ppm.

Multiply however many ppm you want to increase by 1.75.

Example: you are at 420ppm and want 450ppm (30ppm increase needed) you would 30ppm X 1.75 = 52.5ml