Water changes vs. Ca. & Alk

aussiereefer82 · 10-11-2005, 09:25 PM

I know i know.........another about calcium and alkalinity, but this one is different i promise.

I try to maintain my system around 420ppm calcium & 10dkh alkalinity. When i do water changes i use NSW (natural sea water) and it tests at around 400ppm ca. and 7dkh for alk. Now if i change 20% (i do this weekley) this will drop the alk of my system right?? (tank is 10dkh and 20% replacement water is 7dkh)

I assume to combat this i could add baking soda to the NSW to bring the alk up, but what will this do to the ca. of the NSW?? Will it drop??

Should i be adding both a calcium and alkalinity supplements to the NSW to obtain the levels that i want?? If so how much of each should i add to 10gals of NSW??

Hopefully one of the chemistry gurus (Tom) can answer my questions and hopefully you aren't as confused as i am.

Thanks.

Loverotties · 10-11-2005, 11:07 PM

Theres probley a calculation,but just wanted to tell you I add both to my system using NSW!

Pez Vela · 10-12-2005, 01:11 AM

That is a tough one! Being located in Oz, are the animals you have in your aquarium native or semi-native to the reefs around you? (ie: indonesia) The reason I ask is that I would think whatever levels are found in your natural seawater would be ideal for the inhabitants. I would not want to alter the levels that are found in nsw. The water changes should be more than adequate to maintain levels and I would forget about adding anything foreign. I ran a calculation on a reef chemistry program and it came up with 8.2 dkH as the balanced alkalinity for water with a Ca reading of 425ppm & 7.4 dkH for Ca readings of 400ppm. It appears the readings you are getting from your nsw are right on the mark for perfect water!

The Ca will obviously drop in a contained environment by animal consumption etc... but the weekly water changes should keep this replenished. I think you should leave your alk level alone since there is no better proper level indicator than mother nature. If it reads 7.0 right out of the ocean, then leave it at 7.0 Maybe just larger water changes or even more frequent based on animal load. I wish I had nsw to use!

Mike

ps: did a skip through Sydney, Cairnes & Port Douglas not too long ago and from what I saw and experienced in the country and with the people, you have every reason to be a "Proud Aussie"

skeety · 10-12-2005, 07:10 AM

add a top off kalkwasser drip to your system, and all that becomes a null issue.

your water change might drop your levels a bit, but the drip will compensate, keeping everything perfectly in check.

look into it. Kalkwasser is almost magical when it comes to it's abilities to keep your Ca and Alk levels exactly where they are when you start a drip.