Saltcorner
By Bob Goemans
By Bob Goemans
Hi Bob,
I urgently need your advice! My 100 gallon tank is plenum equipped, and uses an aragonite sand. I also employ a calcium reactor (with ARM media) with no other additives or limewater. The tank has worked well so far, except for a slightly low KH. The pH at the moment is ranging from 7.95 to 8.18. The tank is full of stony coral. I note that some stony corals are "melting" at their bases. I checked the parameters and find that the KH is as low as 4.4 and the calcium is at 340!
The calcium reactor works well so far and I also check the effluent/output. The manufacturer of the reactor recommended that about 60 - 100 drops of water output per minute would be fine. I tested the result of this and noted a KH of about 40. However, I do not work my reactor in accordance with the direction of the manufacturer as I simply do not find sufficient output to feed the requirement of my tank.
My way of dealing with the reactor is that I increase the output of the reactor to the extent that the output will be 20ml per minute at a pH of 7.3 (bearing in mind that the ARM will melting at pH of 7.5). Even the output water has only a KH of 9.6 and a calcium of 400, I do think that the aggregate sum of carbonate and calcium generated by this means will be far greater than 100 drops of super saturated solution as recommended by the manufacturer. Am I right?
On my direction to handle the reactor, I still find that the KH in the tank is gradually dropping and to 4.4 at the moment. I think that because I house many stony corals, the input of carbonate, etc. is far less that the consumption rate which lead to a gradual decline of the KH in the tank and further to the extent that the depiction of carbonate in the tank affect the growth of the stony coral. I do not have the opportunity to check the magnesium at the moment.
My questions being:
1) What is the safe method to rebuild the KH without damaging the equilibrium so as to halt the stony coral "melting"?
2) What is the long-term method to keep the KH and calcium at a reasonable or NSW level? I note what you wrote in one of your booklets and started to use a calcium reactor for more that half a year without adding other additives. However, I cannot hold the KH and the calcium level firm so far.
3) I am adding a KH buffer additive solution into the tank at a very slow manner hoping that the situation will be improved, does it work or safe to do so?
Look forward to your early reply.
David Wong
Hong Kong
Hi David,
As for your words "melting" I wonder about water movement in these areas. I've had similar type situations when the overall coral mass had increased greatly and caused a reduction in water flow at the base of those corals. Pruning and increasing water flow, besides careful monitoring of alkalinity and calcium resolved those problems.
As for calcium reactor effluent rate, it's mostly predicated on the "volume" and "type" of media in the reactor! It's why I recommend a duel column reactor and/or a very large column if it's a single column reactor, no matter what the size of the aquarium. Better to have control and deliver what's needed, than constantly fight the battle of changing CO2 rate and effluent drip rates, which often occurs with small reactors on large systems!
The goal with calcium reactors is to provide a "minimum" effluent reading of 12 - 15 meq/l or about 36 dKH. Depending upon the size of the aquarium and the draw on the systems alkalinity base/calcium, that reactor and its media with "X" number of drops per minute (whatever they are) at this minimum alkalinity level, may be enough to maintain the "system's" alkalinity at 10-12 dKH or about 4 meq/l alkalinity level. Which is ideal in my opinion. If system alkalinity and calcium levels are not maintained with the recommended effluent parameter, then enriching the CO2 bubble rate may increase the effluent dKH level. If so, the effluent drop rate can be enhanced, yet its dKH level should not fall below the recommended minimum level. If increasing the CO2 does not increase the level of alkalinity in the effluent, the answer is not to increase flow because you can only get some much juice out of an orange no matter how many times you squeeze it!
And when its comes to drip rate, there's no such thing as a given number of drops per minute. They will be whatever they will be to deliver the required parameters. Only time tells if the best any calcium reactor has to offer will keep pace with system demands. This is definitely a case of bigger is better! And in your case, it appears the reactor may be undersized.
Whatever the effluent drip rate, it will be whatever will supply a flow of water containing an alkalinity that is in the range of 3 to 4 times the desired 'alkalinity' of the main system! And that's not happening when you increase flow to 400 drops per minute in your system. Even the calcium level in the effluent is far below what it should be. I would guess you're calcium usage is probably at least 30 ppm per day, and if only 400 ppm is in the small amount of fluid going into your tank everyday, the level of calcium in the aquarium will slowing become depleted.
Go back to the ranges noted above and with a CO2 bubble rate of about 60 bubbles per minute, slow the effluent drip rate until you have the best possible dKH level (keep in mind the minimum mentioned above). If that drip rate is under 100 drops per minute, get a new reactor or at least try installing some new media.
Keep in mind the CO2 bubble rate does impact the dissolution rate of the media, however, ARM and the Knop brand media need very little pH reduction as it dissolves somewhere about 7.8 - 8.0 pH. With a pH lower than that, the amount of dissolution increases, and the effluent rate can be reduced (if needed), however, so does the life span of the media. If anything, as the media becomes worn down, there will be less and less useful alkalinity, and sometimes even a major increase in CO 2 won't help. It's simply time to change the media. And, if you wait too long or use a cheaper/inadequate media, there will be a very large gap between the amount of none useful carbonates and calcium delivered to the aquarium. Carbonates will increase, however, calcium will decrease. That's not a good situation for balanced coral skeleton growth.
You can monitor this value by testing a sample of the effluent when the media is new, and then down the road six months later. You will notice a reduction of useable calcium in the test sample even if the meq/l or dKH levels may be equal! Interesting, but a fact.
There is a new and quite interesting calcium reactor that I've just seen. There's a new type "fluidbed" reactor on the market, and if interested, contact me. Could be the future in calcium reactors is here! A Kalkwasser drip would also benefit the system. I would not add separate buffers as they can upset system chemical balances. Either a new reactor, new media, or add the Kalkwasser drip. Either way, your present reactor appears to be inadequate for your size system.
Hope this helps my friend.
Cheers,
Bob
