trace elements

[esoxlucius]

I don't think any of us need to worry too much about our fish getting all the essential micro nutrients and minerals they need from water because we all do our water changes to keep the nitrate down and minerals replenished. Essential trace elements such as iron, iodine, phosphorus, potassium, calcium, copper, zinc, magnesium, sodium, selenium, and the list goes on and on.

However, for one minute, let's just say that the main reason we all do our water changes (prevention of nitrate build up), is off the table. A new and wonderful bacteria evolves that can deal with nitrate in the presence of oxygen. So a lot of hobbyists think, quite wrongly, that water changes are no longer required.

In this scenario it got me thinking, asking questions that I couldn't find any answers to. Question being....what are the typical absorption rates of the above, and other, trace elements? For instance, how long would it take your stock to fully absorb the amount of any of the above mentioned elements in a freshly replenished tank full of water after a water change? The levels of each element are going to be different, the fish will require more of one element than another, do fish give off some trace elements as a by product of the metabolism processes going on in their bodies? Which elements would run out first without a water change?

Probably right up the street of a marine biologist this one.

 

[RD.]

Not all water sources contain all of those minerals, some are almost void of mineral content. Most quality pellet foods contain a vitamin/mineral premix, so unless one is feeding strictly fresh/frozen, no worries. In the case of the latter best to presoak the food in a liquid vitamin designed for fish.

 

[esoxlucius]

Which types of water supply would be void of all, or most, of those elements? A typical water report seems to list no end of "goodies" to benefit the fish. I also read somewhere that some of the elements work against each other and that an abundance of one element can inhibit the absorption of another. I soon got lost in it all, it's a very interesting subject and very complex when you start getting deeper into it.

 

[RD.]

Areas where the source waters are a combination of rainfall and snow melt. These types of supply water result in very soft acidic water typically defined by low amounts of dissolved calcium and magnesium, and in some cases may be quite low in overall mineral content. While some municipalities may treat the water before it's distributed, I would personally never rely on "essential elements" to be supplied via my tap water. Not only can these elements be hit or miss, including being seasonal for some, their biological value to a finfish via absorption will also be hit or miss to an extent. Far easier, and better for the fish to get these elements from their diet. Even then their biological value can vary among species.

This exactly why public aquariums, zoos, etc, all supplement the diet of their captive fish, unless of course they are pellet fed.

 

[Coryloach]

Generally, fish that come from soft water habitats have adapted to very low conductivity(dissolved ions) so their requirements for any minerals are also low.

I don't know the mechanism of how fish get their minerals from water and the levels required or detrimental to them. It is probably species specific but in terms of plants, in soft water, availability of trace minerals such as iron, boron, copper, zinc, etc..is higher due to the lower pH levels making those dissolved in the form of ions. So it is not just the presence of them but the form in which they're available that matters.

If you have really soft water that is also rich in metals, theoretically they can reach toxic levels. It's one of the reasons why lowering the pH of one's mineral rich water is not the same as using RO water when it comes to soft water fish...

In hard water the opposite happens, and trace minerals availability is generally poor. In my hard water for example I've always had an issue with iron availability to plants(bleached new growth and stunting) and I've got to dose it from time to time. I've been using red clay pebbles as substrate for my emersed plants and the anoxic zones in the roots overcome that issue as they make iron available via the roots. If dosing via the water column, one needs to use a specific form of iron in hard water.

Macro elements such as calcium and magnesium are better available in harder water and their availability is also pH dependent. In low pH, even if the water is rich in calcium and magnesium, critters like snails will still be affected as calcium for example will not be available in a form they can use, and they can and will die with pitted shells....Fish that have adapted to hard water are also unlikely to survive in soft water for the same reason although the opposite is not true. Soft water fish are much more likely to do well enough in hard water. Take for example discus, they can do well enough in hard water but who would keep malawi cichlids on RO water?

Additionally, trace elements and macro elements can affect each other's availability directly as well but probably not enough to affect fish although it can certainly have an effect on plants.

 

[RD.]

It is absolutely species specific, and with fish is for sure a balancing act.

Lots of info on the net regarding this subject, here's an interesting paper from 2016.

(PDF) Water as a source of macronutrients and micronutrients for fish with special emphasis on the nutritional requirements of two fish species: The common carp (Cyprinus carpio) and the rainbow trout (Oncorhynchus mykiss)

PDF | In contrast to terrestrial animals, fish can ingest minerals from food or directly from water. Although micro- and macro-elements are needed in... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

This portion under Iodine caught my eye, 15-20 years ago I ran across someone on a cichlid forum that had an N. venustus (a carnivore in nature) that had a large growth in its mouth, to the point that it could no longer eat. The owner was at a loss and was looking for help. I recommended trying an iodine supplement in the water and see if that helped. I don't recall the exact timeframe, but I believe that within approx. 2 weeks of supplementation the growth disappeared, and his fish was once again eating.

"Hyperthyroidism (goiter) induced by iodine deficiency is more frequently observed in carnivorous than herbivorous and omnivorous fish. (WatanaBe et al. 1997)"

I also recommended that he switch brands of pellets, or at the very least add another brand that I knew contained an adequate amount of iodine in the raw ingredients. (kelp/algae) Last I heard/read his fish was healthy and doing well.

 

[Ulu]

Fish goiters? I never would have imagined that. Just like fish drinking. They don't all drink, but it's tough to believe.

My understanding is that fresh and marine species get their water in a completely different manner.

Fresh water fish absorb water by osmosis through the skin and don't drink or excrete much water. They are retaining minerals by nature.
Marine fish drink and excrete constantly, in a battle to excrete excess minerals of seawater.

 

[RD.]

Yes, and as stated in the paper that I linked to excessive dietary intake can also
lead to thyroid dysfunction, so all of this is a balancing act.

My main concern when replenishing minerals from a water change, is replenishing my buffering capacity, or total alkalinity. (KH)

 

[Rwbpanda]

Nice thread, following