I agree it may contain some metals......who is to say that any other sodium bicarbonate will be totally clean.....you won't unless they are providing a metals analysis with the product. I would check the source of the aluminum scare.....let me know where you read this Doug. Thanks Brad

Below is a material data sheet based on the Arm & Hammer product. They may not have to show any metals here though.

http://www.earthclinic.com/Remedies/....html#ALUMINUM

http://www.hescoinc.com/msds/armandhammer.html

So if you are concerned about A&H baking soda you better read Randy's list of things that contain high amounts of Aluminium. Look at all the amounts in the food you feed your fish.

http://www.advancedaquarist.com/issu...y2003/chem.htm

Informative read
Thank you

Thanks guys. I'm totally at a loss for what's happening. Two of the colonies that are dying are ones that I've had the longest and have always done well. The only other thing I can think of is that my strontium levels are really low, I just tested and there doesn't appear to be any strontium in the water. I'll try lowering the dKH over the next few days and see if that helps anything

Could a lamp be shifting it's colour spectrum?

I toasted 2 large acro's when I didn't catch my bulbs going bad.

Have you tested you alk with another test kit just to be sure? I find aged alk test kits will give you false readings. Do you run any phosphate removal media in conjunction with bio pellets and carbon? If you do, be cautious, this three combination will strip your water "clean" and if all changed at the same interval, it will shock sps. Finding the right balance takes a little practice, something to think about.

I don't use a phosphate product, which is why I think cyano is exploding now that I have the biopellets in there (I read somewhere that cyano does well in a low nitrate/high phosphate environment).

I am using a seachem test kit that's about 6 months old. I've been testing for total alkalinity, just did the test for borate alkalinity and discovered that my carbonate alk is actually about 7.28, so on the low side.

I also picked up a much better pH test kit, and it's also lower than I thought, around 7.8-7.9.

Spent the morning reading about water chemistry, and I think I really should have been baking my baking soda first to drive off that extra hydrogen. I think it's caused my pH to fall too low for some of my colonies, ones that I assume are more sensitive to pH (some are doing just fine). I just spent the last hour baking my baking soda and made a new batch of top off solution. Going to do a water change now and see if things improve over the next few days. Hopefully they do as the burning colony has survived all my other trial and error learning experiences, I'm kind of attached to it.

Personally I would shut your reactors down and do a water change till things recover. At least it will eliminate one possible source of the problem...

Just an update:

I ditched my straight baking soda dosing solution and replaced it with baking soda that had been baked at 320 degrees for a little over an hour. Sodium carbonate it a heck of a lot less soluble in water than sodium bicarbonate, it turned in to a solid block as soon as I poured it in to the water. It took nearly 20 minutes to dissolve it all.

I also did a water change and added some seachem reef buffer (which I believe is a borate based alkalinity booster), enough to bring my pH up to 8. The decline of my coral colonies appears to have stopped, with one showing marked improvement over the last couple of days.

I'm noticing that the colonies that were hardest hit are acroporas with very similar body and polyp structures, just different colours. I'm thinking they might be more sensitive to pH than the other species I have.

Now I'm going out of town for 4 days, here's hoping all my automation stuff works like it's supposed to and i don't come home to a total disaster.

i bake my bakign soda as well.