"If a sudden low pH spike liberates high metal levels, then you're suggesting in some tanks pH's will drop to very, very low levels.
No, not very low. Anything from about 6.5 or lower, and these levels will commonly occur if there is, for example, a malfunction of the regulator for a calcium reactor, or ....
How do you form the opinion that "these levels will commonly occur"? A calcium reactor, with approx. 5 lbs. of crushed coral or aragonite and one gallon of water, runs at pH 6.5 to 6.0, and contains, approximately, 1.5 gallons of water. If this unit services a tank of any volume greater than 5 gallons, containing coral, live rock and, possibly a DSB, how do you envision this "dynamite" 1.5 gallons of water reducing all of that system (say a 55 gal. or larger tank with 50 lbs. of live rock and possibly a DSB) to a pH equivalent to that of the calcium reactor which malfunctioned??? Have you seen this happen very often????? Has anyone reading this ever heard of this happening????
"The capacity of a tank to detoxify materials is finite"....
By this statement, I gather you believe that a tank DOES detoxify the salt water that is added. The data that you DID provide, as minimal as it is, substantiates that statement. Assuming that it is not the mere existence of fish or invertebrates that detoxify the incoming water, than the remaining detoxifying systems are the DSB and the live rock. Is there some other system that could be doing it?? If it IS the DSB and the live rock, why would you suggest that people remove the very systems that are, in reality, purifying the water that they are adding??? If one takes out the DSB and live rock, what is left to "purify" the incoming salt mix????
"by my math I see an IMPROVEMENT in the water quality by NOT changing the water.
Sure... as long as there is some export, and that export doesn't involve much removal of salt, you are far better off not add new salt water, but simply to top off with good RO/DI water. More about this in the next article.
The problem comes when you have to replenish salt.... "
Why is there a problem when you have to replenish salt???? If the salt water in established reef aquaria is purer (regarding heavy metals) than the salt water being added, that does not mean there is heavy metal "export" from the system. It means that the heavy metals that are being added in the salt water are being sequestered or segregated from the water by some mechanism which is critical to reef aquarium success. In all likelihood, that mechanism is the formation of sulfides in the DSB or in the live rock.
""Instead, I believe the hydrogen sulfide present in DSB's ties up any metal in sulfides, which are NOT soluble at any pH's found in reef aquaria.
As long as they remain anaerobic, this is the case. Once the sediments become aerobic the sulphides will go to sulfates and they will become soluble. ""
That is not, from a chemistry perspective, the way things work. For example, The smell of rotten eggs (a typical fart), is hydrogen sulfide. Exposure to air, becoming aerobic, does not change it to hydrogen sulfate. Silver tarnish is silver sulfide. It's on the outside of silver items due to exposure to impure air. It does not wash off with water because it's silver sulfate. Heavy metal sulfides have solubility products which indicate extreme resistance to being dissolved. Even if, somehow, a reef aquarium of any size somehow dropped to pH 6.5, they would not suddenly "explode" into the environment. Reef aquarists complain of pH's below 7.8 or 7.9, yet you feel that pH excursions into the 6.5 range are, apparently, commonplace. ??????????
One critical issue in this discussion is whether or not established reef tanks have lower levels of heavy metals than the salt water mix being used to create and replenish them. If the new water DOES have a higher level than the water in the tanks, than the tanks have natural detoxifying systems which are enabling us to have the systems that we do. To remove those detoxifying systems (DSB, live rock, coral) and incur a tremendous expense based upon such limited data, especially when that limited data implies that those systems IMPROVE water quality, makes no sense at all.
It DOES make sense to replenish the removal systems (new sand, for example), and minimize introduction of new toxic material -using NSW when possible for example. But- ripping everything out- DSB, rock, coral - when a lot of what would be ripped out is helping us succeed, makes no sense.
No, not very low. Anything from about 6.5 or lower, and these levels will commonly occur if there is, for example, a malfunction of the regulator for a calcium reactor, or ....
How do you form the opinion that "these levels will commonly occur"? A calcium reactor, with approx. 5 lbs. of crushed coral or aragonite and one gallon of water, runs at pH 6.5 to 6.0, and contains, approximately, 1.5 gallons of water. If this unit services a tank of any volume greater than 5 gallons, containing coral, live rock and, possibly a DSB, how do you envision this "dynamite" 1.5 gallons of water reducing all of that system (say a 55 gal. or larger tank with 50 lbs. of live rock and possibly a DSB) to a pH equivalent to that of the calcium reactor which malfunctioned??? Have you seen this happen very often????? Has anyone reading this ever heard of this happening????
"The capacity of a tank to detoxify materials is finite"....
By this statement, I gather you believe that a tank DOES detoxify the salt water that is added. The data that you DID provide, as minimal as it is, substantiates that statement. Assuming that it is not the mere existence of fish or invertebrates that detoxify the incoming water, than the remaining detoxifying systems are the DSB and the live rock. Is there some other system that could be doing it?? If it IS the DSB and the live rock, why would you suggest that people remove the very systems that are, in reality, purifying the water that they are adding??? If one takes out the DSB and live rock, what is left to "purify" the incoming salt mix????
"by my math I see an IMPROVEMENT in the water quality by NOT changing the water.
Sure... as long as there is some export, and that export doesn't involve much removal of salt, you are far better off not add new salt water, but simply to top off with good RO/DI water. More about this in the next article.
The problem comes when you have to replenish salt.... "
Why is there a problem when you have to replenish salt???? If the salt water in established reef aquaria is purer (regarding heavy metals) than the salt water being added, that does not mean there is heavy metal "export" from the system. It means that the heavy metals that are being added in the salt water are being sequestered or segregated from the water by some mechanism which is critical to reef aquarium success. In all likelihood, that mechanism is the formation of sulfides in the DSB or in the live rock.
""Instead, I believe the hydrogen sulfide present in DSB's ties up any metal in sulfides, which are NOT soluble at any pH's found in reef aquaria.
As long as they remain anaerobic, this is the case. Once the sediments become aerobic the sulphides will go to sulfates and they will become soluble. ""
That is not, from a chemistry perspective, the way things work. For example, The smell of rotten eggs (a typical fart), is hydrogen sulfide. Exposure to air, becoming aerobic, does not change it to hydrogen sulfate. Silver tarnish is silver sulfide. It's on the outside of silver items due to exposure to impure air. It does not wash off with water because it's silver sulfate. Heavy metal sulfides have solubility products which indicate extreme resistance to being dissolved. Even if, somehow, a reef aquarium of any size somehow dropped to pH 6.5, they would not suddenly "explode" into the environment. Reef aquarists complain of pH's below 7.8 or 7.9, yet you feel that pH excursions into the 6.5 range are, apparently, commonplace. ??????????
One critical issue in this discussion is whether or not established reef tanks have lower levels of heavy metals than the salt water mix being used to create and replenish them. If the new water DOES have a higher level than the water in the tanks, than the tanks have natural detoxifying systems which are enabling us to have the systems that we do. To remove those detoxifying systems (DSB, live rock, coral) and incur a tremendous expense based upon such limited data, especially when that limited data implies that those systems IMPROVE water quality, makes no sense at all.
It DOES make sense to replenish the removal systems (new sand, for example), and minimize introduction of new toxic material -using NSW when possible for example. But- ripping everything out- DSB, rock, coral - when a lot of what would be ripped out is helping us succeed, makes no sense.
. Here are some of the links:
