Make up water dropping Alk/Ca

[spaulr]

Background -

40 gallon - 55-60 gallons total
Daily dosage of Randy Farleys Ca and Alk solution of ~15ml each
2 small SPS corals (added last Wednesday)
1 4" lobophyllia (3 week resident)

Did a water change 2 days ago.

Ca - 450
Alk - 12 dkh

Yesterday my Alk measured 9.5

Is my make up water (RO/DI) causing the significant drop in Alk - even with the daily dosing? I didn't bother measuring Ca. My tank evaporates probably 1-2 gallons a day.

 

[Anonymous]

Most likely yes, if you've been religously dosing that 2 part, and that Alk (12dkH) is constant over the time, then I would say the culprit is infact the make up water, especially if it's a rather large volume and/or little alkalinity in the new water.

Now it is true as corals grow over time their consumption increases, and as such you must increase the amount you suppliment your tank with, however if you got those original readings a week or so before rather than 3 months ago, then yeah, water change did it. Simply mix up some new water and test it next time.

 

[spaulr]

The water change water (with Instant Ocean Salt) actually tested out at 12dkh Alk (I'm sure the Ca level is low, but wanted to focus on one thing at a time). I didn't bother testing Ca, as I'm only attempting to get my Alk level over in between water changes. Do you added Alk and Ca supplementation to the DI make up water prior to adding it to the tank?

 

[Anonymous]

Do you added Alk and Ca supplementation to the DI make up water prior to adding it to the tank?
I don't no, mostly because it'll precipitate most likely.

That's strange about the IO having a high Alk, only thing I can really think is one of your other parameters is out of whack and giving a false reading.. *shrug* I'm not a chemical expert with this though.

 

[spaulr]

Possibly. I'll retest it on the next water change. I definitely KNOW that Instant Ocean is low on CA (325-350). I'm using ELOS test kits for Ca, Alk, and Nitrate. They're a lot more readable than Salifert kits.

Hmmm. So, how do you account for top off water effecting your Alk/Ca parameters? Or do you know from experience that you need to over dose by X amount to get the correct Alk/Ca combination?

Thanks for your help by the way!

 

[Anonymous]

Yeah I'd retest every batch, I once had a batch of IO which had incredibly low alkalinity. Could have just been a bad "batch"

So, how do you account for top off water effecting your Alk/Ca parameters?

In general it basically dilutes both. Now I know people will say "BUT BUT BUT when evaporation occurs only water leaves" which for the most part is true, however if you test prior to a top off, you're testing the same amount of "stuff" in a lower volume of water, now will it give you a swing of 2.5 dKh? not likely unless you lost 20% of your volume to evaporation.

Specifically though, it doesn't do much to affect anything, unless of course you simply use tap water with a dechlorinator or something, then the hardness of your water could translate to additional calcium/alkalinity in your system... atleast as read on a test.

 

[trido]

Have you tested you Alk. during the week without doing a water change? It is possible that you need to dose more solution on a daily basis.

Although, with only two SPS frags/colonies, I doubt they would be sucking up that much.

 

[Anonymous]

urk... yeah another thing to ask is did you test at the same time of day? Alkalinity readings can easily fluctuate with pH changes

 

[spaulr]

Good point. I haven't been good about testing at the same time during the day. That could be part of the problem. I'll remember to do that. Typically, I add the Alk and Ca parts in the early morning before lights come on, and test in the evening when I get home from work (lights on in full force).

My Ph seems to stay around 7.9-8.1.

It's very possible that I'm not dosing enough of the mixtures. I'll up the dose a bit and keep testing alk for the next few days.

 

[saltank]

I'll add my experience here. I also use IO and yes ime it is low in calcium but alk levels have always tested fine.

I just had a battle with adjusting my calc and alk levels in my 46gal with 14gal sump. Part of the problem was that I was testing at all different times. I started testing after I got home from work in the evening and performing two tests each for reliability, then adding buffer and retesting about the same time the next day. It took about two weeks to really get where I wanted (calcium 420-440 and alk approx 3.7-3.8). This way I was also able to determine how much buffer and calcium supplement is required in my system to raise the levels a given amount.

As for messing with the levels in the make up water, I don't do it. I perform slightly less than 10% wc every other week. When I tried raising the calcium level in the io makeup water the paramaters went bonkers (both alk and calc ended up so out of whack I dumped the entire batch and started fresh).

That is just my experience. I drip kalk pretty much constantly to maintain the parameters in the tank.