Testing Synthetic Seawater Against Natural Seawater

A couple of recent comments from users of natural seawater (NSW) started some questions in my mind. One question led to another and I ended up trying to think up a reasonably accurate way of proving the best. With NSW the question of potential pollution and the need for transportation and storage is ignored.

The heading may on first thoughts seem strange. Mother Nature provides the seawater on the wild reefs, and that is where the majority of our livestock comes from. So it follows that NSW must be best. Yes it does and it is – on the wild reef. It may well be best in the aquarium as well. However, in the natural world the seawater has, to all intents and purposes, an inexhaustible supply of, for example, calcium. Huge amounts of seawater are available and this washes the reef. All the other seawater contents are available in the same way.

In the aquarium the amount of seawater is obviously restricted. Therefore, even if the NSW was perfect to start with the demands of a hard coral captive reef would deplete some of the constituents, again for example calcium. This is why so many aquarists use additives, or calcium reactors and the like.

Synthetic salt mixes are of a very high quality nowadays. They don’t fully equate to NSW, as, to my knowledge anyway, there isn’t a manufacturer who can create a salt to that accuracy. Because of the demand for the example calcium in an aquarium, some manufacturers boost this. Nevertheless, aquarists usually need to supplement to maintain desired levels. In addition, many aquarists maintain a higher alkalinity level to resist the higher acidic pressure within the closed aquarium.

So in my mind NSW is best, I have no doubt, at least to start with. But what of ongoing use, what then? How could it be shown one way or another?

I suppose the only way to show any difference in the ongoing use of the two types of seawater would be to use them both at the same time. A great deal of care and discipline would be needed. I am not a scientist and have not had any scientific advice, but if such advice were forthcoming it would no doubt be that in any trial all possibilities of unwanted influence must be removed. Otherwise at the end of the trial arguments could be made that X caused this in NSW but was not available to synthetic, and so forth.

So the trial would be something like this. A scientist might well find holes, but here goes anyway.

Two equally sized aquariums (they wouldn’t need to be very large) would be obtained. Sumps would not be necessary. A reef would be built in each aquarium, but not out of any type of rock. Rocks are too variable in size, shape and weight. Therefore a structure, exactly the same in each aquarium, would be built to support any corals. This would equalize gallonage in each system and hopefully circulation.

Remembering that this is a trial to show which seawater is best for livestock, equipment would be fitted to maintain water quality. An efficient protein skimmer of the same make and model would be fitted to each aquarium. So would heaters of the same wattage, to maintain each system at the same temperature. The lighting system, metal halides probably, would light each and be exactly the same make of bulb, the same power and spectrum. Circulation devices would be the same make, model and power. Additives for the example calcium would be available from the same manufacturer so that the amounts being added could be recorded during the trial. Any other additives would also have the amount recorded. When additives were used, each system would be kept at the same level.

The equipment mentioned above would be fitted inside each aquarium in the same place. The lights would be the same distance from the water surface.

The two aquariums would need two logs, so that they could be compared at the end of the trial. These logs would cover at least weekly tests on the same day of all the normal reef aquarium parameters checked for. Temperature would need to be recorded also.

Evaporation would be physically topped up with reverse osmosis (R/O) water from the same R/O filter, always ensuring that the level ended up correct. I assume there would be no point in recording the amounts required for these top-ups.

Then we come to the standard practice of routine water changes. In a trial such as this, normal practices would need to be followed. So each week 10% (or whatever agreed percentage) would be changed, NSW for NSW and synthetic for synthetic (using the same make of salt as used at the fill of the aquarium).

Then there is stocking – an aquarium without livestock is not going to prove much. Perhaps there would be a cleaner shrimp or two in each aquarium. Fish would be introduced to the full recommended level for a captive reef system. The fish in each aquarium would be the same, as far as possible the same size. Corals are more difficult, but again each aquarium would be as far as possible fully stocked with the same type and size of coral (not so ‘easy‘).

Feeding would of course need to be sufficient for the proper nutrition of the livestock. The food that entered each system would be measured by weight and of the same type at the same time. The food would be from the same source and/or manufacturer.

Routine maintenance in addition to water changes would be the same and thorough on each aquarium – skimmer cleaning etc.

At the end of the trial period each aquarium log would show a history of the coral growth and colour, fish health and any particular livestock points of note. The tendency of the seawater would have been recorded over time for each aquarium, and would indicate calcium demand, nitrate build up, pH, alkalinity changes etc.

Out of this attempt to run an unbiased trial, it would be the livestock that would be paramount. The livestock would be the judge and jury. If one reef was clearly better than the other then there would be the answer. Also available would be the information about how much additives had been needed in each system, giving an indication of cost (on top of lighting, heating etc).

Then aquarists would know which is the better for a captive environment. The unbiased trial figures would be there to see.

Mind you, in scientific circles there always seems to be argument about any trial. If the result favoured NSW, synthetic salt manufacturers would claim it was because their particular salt had not been used. But the above, to my untrained mind, seems reasonable.

What do I think would be the result of such a trial? As an out and out guess, I would say they would be more or less equal. I have always believed that NSW is the best – but seawater degrades/changes in a captive system. I think it was Dr Ron Shimek who stated that systems he had tested ‘bore no relation’ to real sea water. So synthetic or natural, they would both need supplementing after a time with a percentage of new seawater plus additives.

There are two questions that remain though that – just maybe – could tip the result. The first is that newly mixed synthetic seawater is ‘harsh’ and dead even though it has been mixed for hours in a bucket. NSW is, well, natural, more ‘pleasant’ perhaps for the livestock. Would that make a difference? The second is that NSW is ‘alive’ – is there something there that would make the difference, something synthetic doesn‘t have?

Professional testing as above is not going to happen. The synthetic salt manufacturers have no interest for obvious reasons, and the scientific community has no interest from the ‘what to use?’ point of view.

Transportation and storage are obvious concerns for the use of NSW (disregarding potential pollution). Most hobbyists are happy with their captive reefs and the use of synthetic salts. Some of the photographs of these systems show what can be achieved.

Is there an aquarist who has the money, space, knowledge and discipline to have a go? I’m sure there’ll be silence, as aquarists enjoy the hobby, achieve for the most part success, and haven’t the desire to go ’scientific‘.

Wouldn’t it be great though, if an aquarist stated That’s been done, here’s the records. The result was clearly…..!


Testing Synthetic Seawater Against Natural Seawater
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