Alk too low in CA Reactor

[DA Mini reefs]

Help anyone
I've been useing an Aqumedic CA Reactor for over 12 months now.My effluant PH is stable at 6.6-Cal 400 Kh 80!! only. If I set the eff Ph to range between 6.2-7 the Cal is 480-350 BUT Kh still is only 80-100. Coraline algae not growing much, corals seem to come out more with Cal 350 Kh 100 than Cal 480 and Kh 80. Tank is 4x2x20inch high.I don't want to have to supp with Kh buffer all the time and I was told this reactor would "look after Cal and Kh"?? Is a low Kh of 80ppm[4.5dkh] going to be a problem long term? Media in the reactor has not gone down much at all in 12 months. How do I know when the media needs to be changed? Sorry for all the Q's but no one in Australia seems to know much about this problem. Any help would be greatly received.
David

 

[MiNdErAsR]

I assume the calcium and alkalinity readings you listed are for the tank? What are your reactor settings? How many ml/min? Sounds like you need to dial in your reactor. However, and more importantly, you *must* get your alkalinity back in normal range. I would suggest multiple water changes of substantial size.

Once this is achieved we can begin to get your reactor dialed in. Keep a running log of settings, alk & Ca levels, changes made to settings, etc. This will make life easier for you in the long run. Allows you to easily see the trends.

I would suggest a starting point of 30-40ml/min @ 6.70 pH. Measure Alk & Ca for a baseline, then again in 24 hours. Should levels drop off, then increase CO2 feed and retest again 24 hours later. Continue in this fashion until you reach 6.50 pH (or your alk level stabilizes). Should you reach 6.50 pH and alk continues to fall, then increase effluent flow rate by 10 ml/min (or so) and begin again. Continue until desired alk level is achieved and maintained.

Remember to test for alk 24 hours after each setting adjustment. Only change one setting at a time! If you change flow rate, leave CO2 setting alone! At this flow rate it should take ~2 hours for pH to level off after making adjustments.

HTH

 

[DA Mini reefs]

Hi Jim,
Thanks for your interest and advice. I'll adust the settings to what you have said and let you know in about a week's time. Readings are from the tank
Regards
David