siskiou Posted June 5, 2009 Share Posted June 5, 2009 Lately, I can't seem to keep my Alk up. It always drops down to 6-7 within a day, unless I dose hugely with Randy's recipe. My top-off water has Kalk, but that doesn't seem to be enough. I use Reef Crystals, and have for about a year and a half, my pH has actually been high lately (8.3-8.57), Calcium is at 420, MAG at 1300. I was blaming my sulfur denitrator, but I'm only running that on the 120G and the 60G has the same Alk problem. I've been running a phosban reactor with GFO on the 120G and have recently added a HOB with GFO to the 60G. Is that known to deplete ALK? Or how about Carbon? Does that lower Alk? I just can't believe that my little SPS frags would use it up that quickly! Quote Link to comment Share on other sites More sharing options...
Lowman Posted June 5, 2009 Share Posted June 5, 2009 It's not the size of the frags but how many you have in the tank. Have you tested the alk in a fresh batch of water? i personally haven't heard of GFO reducing alk, but anything is possible Quote Link to comment Share on other sites More sharing options...
dsoz Posted June 5, 2009 Share Posted June 5, 2009 Is the test kit bad? I was having issues with "low calcium" until I had someone bring over their test kit and my calcium was actually very high. I had a bad test kit. dsoz Quote Link to comment Share on other sites More sharing options...
impur Posted June 5, 2009 Share Posted June 5, 2009 I found this http://reefkeeping.com/issues/2004-11/rhf/index.php Many aquarists using GFO have reported unusually extensive precipitation of carbonates on the solid GFO, and elsewhere in the system. Such precipitation can, for example, be a contributing factor in the caking of such materials, and can coat other surfaces in the aquarium. This precipitation can also contribute to a drop in alkalinity and possibly pH as it removes carbonate from the water column. The effect of calcium will be similar, but smaller on a percentage basis, with a drop of only 20 ppm calcium for every 1 meq/L (2.8 dkH) drop in alkalinity. Increased calcification by corals and coralline algae (possibly spurred by reduced phosphate) can also cause similar drops in calcium, alkalinity, and pH. Dissolution of these precipitates with acid, accompanied by bubbling, indicates that these deposits are carbonates, and are most likely calcium carbonate since it is supersaturated in most reef aquaria (and in the ocean). Several factors may contribute to this precipitation. Many of these are rather straightforward. It is known, for example, that phosphate inhibits the precipitation of calcium carbonate. Much like the role that magnesium plays in seawater, phosphate binds to the growing calcium carbonate crystals, poisoning their surface against further precipitation of calcium carbonate. Many organic materials are also known to inhibit this precipitation. Near the surface of the GFO, and downstream from it, the organics and phosphate are expected to be lower in concentration than upstream from it. The reduction in concentration of these inhibitors may well permit increased abiotic precipitation of calcium carbonate on such surfaces. Two more esoteric events may, however, be equally important. The first is that the local pH near the GFO surfaces may be higher than in the bulk solution. This effect arises as phosphate and other inorganic and organic ions displace hydroxide from the surface. Figure 2, for example, shows phosphate displacing two hydroxide ions. The net swap of HPO4-- for 2 OH- will raise the local pH. The supersaturation of calcium carbonate increases as the pH rises, driving the precipitation of calcium carbonate. Another possible role may be played by the iron itself. GFO is not completely insoluble. The solubility of iron hydroxide in natural seawater is small, but still significant (0.02 - 2 ppb), although it is largely controlled by the availability of organic ligands.11-13 One interesting possibility lies in the way that soluble iron actually impacts the precipitation of calcium carbonate. At high concentrations, iron inhibits the precipitation of calcium carbonate. While different researchers find different threshold concentrations for this inhibition (>25 ppm in one case,14>7ppm in another case15), it is a well established and studied phenomenon. The mechanism is believed to be the same as for magnesium, phosphate, and organics, which all poison the growing calcium carbonate surface. At much lower concentrations, however, iron actually increases the precipitation of calcium carbonate by acting as a site for nucleation of new crystals. In one case this happened at 100 ppb dissolved iron, increasing the rate of scaling (the precipitation of calcium carbonate on surfaces) by about 60%.14 In another case, the induction time for precipitation (that is, the time it takes for precipitation to begin once the water becomes supersaturated) was reduced by 40% at 1.4 ppm iron and the overall precipitation rate was increased by 32% at 560 ppb (lower iron levels were not tested).15 These studies were carried out in freshwater, and I have not seen similar studies in seawater. Is the natural dissolution of GFO important in the nucleation of calcium carbonate precipitation? I am not sure. But it is clearly one possible explanation that fits the observations of aquarists as well as known phenomena involving iron. Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 5, 2009 Author Share Posted June 5, 2009 I just tested my fresh batch of saltwater, and it's at 11. I don't *think* my testkit is bad, but I'll take a batch to the LFS and see what the result is there. Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 6, 2009 Author Share Posted June 6, 2009 Thanks for the info, Miles! I'm not sure it applies to my tank, since my pH is actually going up, but you'll never know. I haven't noticed any precipitation on the GFO or elsewhere. What I do have is brownish slime algae on the sand, which I was hoping the GFO would help with. Quote Link to comment Share on other sites More sharing options...
impur Posted June 6, 2009 Share Posted June 6, 2009 I have read several times that GFO will reduce alk. I haven't experienced it. But it definately could be your problem. Try testing each day for a week with the GFO running, then remove it for a week and do the same tests. That should tell ya if its the GFO Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 6, 2009 Author Share Posted June 6, 2009 I'll take the GFO offline today, and see how it goes! Do I have to rinse and dry it for the week, or can it stay in the reactor and be used again? Quote Link to comment Share on other sites More sharing options...
impur Posted June 6, 2009 Share Posted June 6, 2009 I'd let it dry out. You never know what can build up in a week. Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 6, 2009 Author Share Posted June 6, 2009 Good point! Will take the GFO offline and rinse and dry. I'll update this thread once I've had the tanks off GFO for a few days to see if there is a difference. Quote Link to comment Share on other sites More sharing options...
chewie Posted June 7, 2009 Share Posted June 7, 2009 Do you have any clams? Those little buggers are ALK sponges! Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 7, 2009 Author Share Posted June 7, 2009 No clams, though I've been contemplating getting one someday. Quote Link to comment Share on other sites More sharing options...
Dego Red Posted June 12, 2009 Share Posted June 12, 2009 siskiou, Keep us posted please. I've been having the same problem lately. I find myself dosing 4x Alk to each part Ca & Mg and can't figure out why. My pH supports my alk readings since they still move relative to one another, so I don't believe my test kit is bad. Like you, I'm also running GFO and carbon in my mixed reef, so I really want to keep at least the carbon. I don't have nutrient issues (NO3 = 3, PO4 =< 0.03) so I could remove my GFO for a bit and see what happens. I never planned on running it and vodka dosing instead, since my nutrients were so low, I just opted for the GFO. Perhaps I'll pick up the vodka bottle again. Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 12, 2009 Author Share Posted June 12, 2009 Along with the low Alk, I'm also having high pH (up to 8.69). LFS readings confirm my test results, though I also have a new pH probe on the way, just in case. I need a second one anyhow, for my other tank, instead of constantly switching from one tank to another. I've stopped topping off with kalkwasser, to not drive the pH even higher, and am dosing Baking Soda for the Alk, and Bulkreefsupply Calcium. My freshly mixed saltwater reads 11dkh, so it can't be the salt. I'm stumped right now. and am just changing things one at a time, and watching what happens for a few days. LMK, if you come up with anything, please! Quote Link to comment Share on other sites More sharing options...
Dego Red Posted June 14, 2009 Share Posted June 14, 2009 Along with the low Alk, I'm also having high pH (up to 8.69). LFS readings confirm my test results, though I also have a new pH probe on the way, just in case. I need a second one anyhow, for my other tank, instead of constantly switching from one tank to another. I've stopped topping off with kalkwasser, to not drive the pH even higher, and am dosing Baking Soda for the Alk, and Bulkreefsupply Calcium. My freshly mixed saltwater reads 11dkh, so it can't be the salt. I'm stumped right now. and am just changing things one at a time, and watching what happens for a few days. LMK, if you come up with anything, please! As I type, my last test for the day is finishing up. Once I'm done, I'm pulling my GFO and resuming Vodka dosing, so the clock starts now. Quote Link to comment Share on other sites More sharing options...
Smann Posted June 14, 2009 Share Posted June 14, 2009 Along with the low Alk, I'm also having high pH (up to 8.69). LFS readings confirm my test results, though I also have a new pH probe on the way, just in case. I need a second one anyhow, for my other tank, instead of constantly switching from one tank to another. I've stopped topping off with kalkwasser, to not drive the pH even higher, and am dosing Baking Soda for the Alk, and Bulkreefsupply Calcium. My freshly mixed saltwater reads 11dkh, so it can't be the salt. I'm stumped right now. and am just changing things one at a time, and watching what happens for a few days. LMK, if you come up with anything, please! There are some good articles on Calcium and Alk at WWM.com. You could try stop dosing calcium and see what the actual demand for calcium is on your system. Mine runs about 390-400 and Alk 8-9, its my understanding that you cant have both High calcium and High Alk as one will drive the other down. If your tank will settle in for a lower Calcium level, without dosing or dosing very little, your Alk may rise back up Quote Link to comment Share on other sites More sharing options...
CA2OR Posted June 14, 2009 Share Posted June 14, 2009 Miles is always good for the info. Quote Link to comment Share on other sites More sharing options...
jason7504 Posted June 18, 2009 Share Posted June 18, 2009 well i have had trouble keeping my alk up too..its usually at 2-3 meq/l..my ca around 420 and Mg 1300-1500..and i have good water quality and i dont think the test kits are bad Quote Link to comment Share on other sites More sharing options...
Dego Red Posted June 27, 2009 Share Posted June 27, 2009 Quick update - After removing the GFO, I've seen no change in my alk patterns, and I keep daily test records in Excel. What I have seen is a massive impact on my SPS, and it's not good. I'm getting STN on the bottom of my acro and cap frags, as well as my digi colony. All my parameters are very solid with minimal swings. Judging by my NO3 readings, the vodka ramp-up hasn't taken effect yet, which means my PO4 could still be at detrimental levels. I can't trust my PO4 test kit (reads only 0.03) - got it for my last tank, before realizing from reading that only a photometer is generally accurate. From a very informative post on RC, I put the GFO back in immediately, as well as continuing to dose vodka. The rest of the tank is healthy as can be. Quote Link to comment Share on other sites More sharing options...
siskiou Posted June 27, 2009 Author Share Posted June 27, 2009 I didn't have any changes in Alk after taking off the GFO (no change in the corals, either), but there was a definite change in the pH. It came down to 8.2-8.4. After putting the GFO back online, pH is again at 8.4-8.6+. GFO doesn't seem to have any effect on the level of cyano/diatoms on the sandbed. Quote Link to comment Share on other sites More sharing options...
Cannedmulder Posted June 30, 2009 Share Posted June 30, 2009 Ok first off what is a GFO? and second if I don't know what one is I doubt Ihave one but I too have a hard time keeping up my hardness. I only dose that and not Calcium because it is so high to begin with. I am happy to hear others have this problem and I am not loosing my mind as COReefer was begining to think I had. But I am unhappy because no one has an answer! Quote Link to comment Share on other sites More sharing options...
jason7504 Posted June 30, 2009 Share Posted June 30, 2009 its granulated ferric oxide and it removes phosphates Quote Link to comment Share on other sites More sharing options...
Cannedmulder Posted June 30, 2009 Share Posted June 30, 2009 Thank you! Quote Link to comment Share on other sites More sharing options...
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