Alk level and the desire to keep sps

[ThaBeast]

I have had my 210g tank set up for about 18 months now and everything has been doing well for some time. I plan to start adding some sps as I have never kept them and think I am ready to try. I have read that most have better luck keeping alk at 2.5 - 3.0 meq/l (7-8.5 dkh). My tank consistently is at 4.0 meq/l (11.2 dkh). I use kalk in my ato, supplement Mg monthly, and Ca when it starts to tickle 400. I use the bulk powders from BRS. I use IO salt and do 15 percent water changes almost every week (haven't missed one since July). IO alk usually tests between 3.5 and 4.0 meq/l for me. Do you think I should worry about the higher alk or just be happy it is stable? If I bring the alk down, how would I do so? My only thought was less kalk in the ato and switch to Red Sea salt. Of course, less kalk in ato means more Ca supplements, but that would be ok.

Just for reference my other params are:
Ca: 440
Mg:1450
Salinity: 35ppt
Temp: 75
Po4: Mailman lost my new test kit
Nitrate: consistently < 2

 

[drainbamage]

I don't think the slightly high alk is an issue, you shouldn't experience irritation from the excessive carbonates in the water. If anything the corals that would experience an irritiation would be the softies and LPS's that it sounds like you already have.

Also, what tests have you used to measure? If you're just using one test kit, use another to ensure that your test kit doesn't just need an offset measurement (i.e. my salifert tests consistently 1dkh higher than the actual amount as found out by using the calibration fluid supplied.)

Edit: Forgot this- Try and look up some posts by Bio-Nut. He's done a great chemist write-up on the reaction of carbonates (alk) and calcium (err, calc) and how they interact in the tank. In his write up he notes that levels above a certain degree (think it was in the 10-11 dkh) range will cause precipitation of your calcium into free forming calcium carbonate. If you're calc is showing stable at all times of 440, I'd be tempted to say your test kit is reading high or else you would be losing calc in the reaction (unless you're adding a constant dose of calc as well.)

 

[NanoNano]

Wow maybe I should start keeping SPS. I can't get my ALK to stay high at all.

 

[ThaBeast]

braindamage--I don't have a lot of faith in my Ca kit as it is an API. I have ordered a salifert Ca kit but the post office lost it and my po4 kit that I desperately needed. I use seachem for alk, the last time I checked it against the reference it was spot on in meq/l. I do believe the test kit results of both based on the amount of build up I clean out of my Tunze powerheads. The kalkwasser in the ato is obviously continually adding Ca. I have been concerned about the levels, but my acans, hammers, duncans, and brains look great (well I have a recent lobo addition that doesn't always look happy but is much better since I changed to mh lighting) so my thought has been not to complain just clean the deposits out of the Tunzes and be happy with the coral growth.

My honest opinion is that once I acquire a few sps pieces that really take off in growth my slightly high alk level won't be an issue--at least that is my optimistic hope. I do have one piece of unidentified encrusting sps that 'hitchhiked' in about a year ago and really took off about two months ago, it is almost three times its starting size now.