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It'sJames 11-07-2008 11:26 PM

New to saltwater - water parameter Qs
I'm starting to buy stuff for my first salt tank, and I'm reading up on how to care for it. Books, however, don't seem to be quite clear on a couple things relating to water parameters. So I thought I would bore you all with some noob questions...

1) What exactly should I test for in this tank? It will be fish only until I think I've got the hang of it. One book I'm reading mentions testing for Iodide - is that necessary? If I'm using RO/DI water, do I need to test for phosphate?
2) Assuming I'm using RO/DI water, which I believe would have a nuetral pH (?), will the salt bring the pH up, or would I have to do something? I'm pretty sure this is a stupid question... so forgive me.
3) Is calsium something that will be in a safe range naturally, as long as I maintain a clean tank, or will I need to supplement? I'm sure this is slightly dependant on other factors also, but I'm just wondering how calcium gets into RO/DI water.
4) What kind of salt mix should I use? I believe that some mixes are more complete and don't require as many supplements, is that true?

- James

onefish2fish 11-07-2008 11:35 PM

1. ammonia,nitrite and nitrate to insure the cycle is complete. pH, alk, calc, mg (all go hand and hand) should be tested at a minimum. phosphate and iodine testing is not as important IMO atleast not in the beginning. however having a test kit for phosphates will let you know if your levels are high or not, and high levels more then likely = unwanted algae
2. the alk in the salt mix should buffer up the pH alittle, i wouldnt dose any pH chemicals for it though, as these seem to be inconsistant IMO.
3. calcium may have to be supplemented depending on how frequent you perform water changes and how big the tank is. calc will be in the salt mix (more of it in a reef mix) but calc, mg, alk, all work together. if one is low the others will more then likely be.
4. i cannot recommend a salt mix. i do recommend buying some kind of reef salt as it has more calc, mg, and alk in it. find a salt and stick with it.

Kellsindell 11-08-2008 09:34 AM

When you find a salt mix just make sure you stick with it and don't do huge change overs. i personally use instant ocean and red sea mix and a few others.

Reef salt i don't recommend until you decied to get some corals otherwise your fish and snails aren't going to take very much calcium out so you don't have to worry about supplimenting. Just keep on your water changes and using RO/DI and doing top off and you'll be fine.

onefish2fish 11-08-2008 09:58 AM

see i could be wrong as ive never had a fish only system, but i would think you would want to have good cal, mag and alk levels because they all work together. if mag is low, then alk and/or cal with be. i would think alk is the more important of the 3 in the fish only system and since they all work together you need to have good levels of all three. i believe alk effects the pH as well.

i could be wrong about this.

Kellsindell 11-08-2008 11:27 AM

You are right, but they all can be lower than in reeftanks because they don't require all the nutrients from the water as corals. they filter feed and fish depend on the food you feed more then the water nutrients. I've had one and i kept the SG lower so that they if i would have had any ick issues it didn't happen because of the lower SG.

Pasfur 11-08-2008 04:29 PM

Water chemistry is water chemistry. The relationship between calcium, magnesium, alkalinity, and pH does not change.

This topic is so complicated i'm not sure where to begin. So much depends on stocking levels and type of filtration. Systems which rely heavily on biological filtration to process waste will have a greater degree of difficulty in maintaining these levels. Systems which are set up correctly, in my humble opinion, using a deep sand bed, live rock, and a protein skimmer, will have less difficulty in achieving stable levels. The removal of organic acids by the protein skimmer, as opposed to the biological processing of organics by a biofilter, goes a long way to allow for stable alkalinity levels.

That being said, to maintain a stable pH and properly balanced ions, you will have to test for alkalinity and calcium. I will point out that it uncommon to have both levels high or both low... it is more common to have one level elevated and the other at the midpoint or slightly low end of the range. This is why we try to keep these levels within a given range, calcium between 360ppm and 500ppm, and alkalinity between 8 and 12 dkh. The addition of calcium, even in a fish only system, should be utilized. My chemisty is not strong enough to explain the cause & effect of this relationship, but i know Steve can elaborate or provide some nice links to articles on the subject.

For any system, i would suggest testing alkalinity and calcium weekly, adding the necessary buffer and calcium addition as necessary to stay within the given range. I would personally add calcium daily and buffer twice weekly. The size of the dose will vary based on your systems test results.

As to magnesium, many hobbyists advocate testing. I have personally never tested magnesium and have no plans to. However, i do biweekly water changes and believe this should be sufficient to maintain a proper level. If the time ever comes where my calcium levels are at the proper level and I am still unable to buffer to a correct alkalinity level, then I will have to reconsider my position on magnesium supplement and testing.

Iodide testing in a fish only system would not be needed. In fact, many in the hobby today do not add iodine or iodide to their systems at all and are more concerned with OVERdosing iodide than not having enough in their systems. I do not personally add iodine to my reef.

As to phosphate, I also do not see the need for testing. Interpreting the results would be difficult. A zero reading could simply mean that phosphate is being utilized by algae faster than it is being introduced into the system, but certainly does not mean phosphate is never present. I use my eyes as my favorite test kit, carefully observing for unwanted algae growth. I take steps to reduce phosphate buildup, such as a daily cleaning of all filter pads and utilizing proper water movement to prevent detritus from settling.

RO water would be helpful in any sytem, but many hobbyists do not use RO in fish only systems. Myself included.

SKAustin 11-12-2008 07:09 AM

Let me try to provide a brief insight on the relationship between Ca, Alk, and Mg. Corals, Coralline algae, and some other animals will use Calcium and Bicarbonate (the primary ion in the measure of alkalinity) ions to develop their calcium carbonate skeletons or structures. That part is pretty cut and dry. The need for supplementation will exist, the question is; To what degree? The amount of necessary supplementation and preferred methods will vary based on the details of your system, the livestock you choose to keep and the development of the livestock.

Calcium and Bicarbonate ions are supersaturated in natural seawater. This means that there are more of these ions in the water then the water can effectively hold. This condition promotes the abiotic (non-biological) precipitation of calcium carbonate. In other words; These ions attach to one another creating a calcium carbonate solid that forms on various surfaces within the system, especially where heat is generated like heaters and powerheads. This is where Magnesium comes into play. Magnesium ions bind to the forming calcium carbonate crystals making them less attractive to the ions and thereby poisoning (stopping) the abiotic precipitation. This is what allows these ions to remain supersaturated in the water column.

pH is also a factor in this cycle. Bicarbonate and carbonate are different forms of the same ion. At lower pH levels, the Bicarbonate is the dominant form. As the pH is increased, so is the concentration of the carbonate form of the ion. It is the Carbonate ion that is a driving factor for the abiotic precipitation of calcium carbonate. To simplify this statement; As the pH rises, so does the rate at which Calcium Carbonate can precipitate out of the water.

For a more detailed explanation of this relationship, and an easy to understand explaination of how Aibiotic Precipitation of Calcium Carbonate occurs, see this article by Mr. Randy Holmes-Farley.

A Simplified guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH

Iodine is one of the supplements that can be very detrimental to your system. Your system will get more than it's share of iodine in the foods, water changes, and even some other supplements. The problem with Iodine is that there are several forms, some of them are toxic, and all of them can introconvert. Test kits available to hobbyists only detect a small subset of these forms, so overdosing iodine is quite common, especially when testing and trying to maintain levels.


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