How Copper Affects Dwarf Shrimp

Today I would like to talk about Copper (Cu) and how it affects dwarf shrimp. This is a very delicate subject because any mistake here can take the lives of our shrimp. Everybody knows that copper is extremely dangerous for shrimp and snails. They are very sensitive to this chemical element. However, I do not take anything for granted. I need to know the details.

That is why I started asking questions. Why is copper dangerous? How exactly does it affect the shrimp? What is the dangerous level for Caridina and Neocaridina shrimp? Is the dangerous level the same for all dwarf shrimp? Unfortunately, popular shrimp blogs and websites have close to zero information about it. Thus, I start the search from the scratch myself (well, this is not the first time I do it) and I have found some very interesting information.

First of all, copper (Cu) is a crucial trace element for shrimp because it is an essential part of their blood. However, copper is also a potentially toxic substance for them. All studies have shown that shrimp are adversely affected when exposed to high concentrations of copper. Exposure to high copper disrupts respiration, inhibits reproduction, reduces fertilization success, decreases fecundity, and puts pressures on the immune systems of the shrimp. The chronic exposure to copper sulphate produced blackening of gills in Caridina shrimp, which can be seen even through the carapace.

The problem is that the limit between the requirement and toxicity of copper is delicate and dependents on a variety of factors.

Copper and Dwarf Shrimp’s Blood

As I have already said, Copper (Cu) is a crucial trace element for shrimp because it is an essential part of hemocyanin. Like a human body needs iron for oxygen delivery in the “blood system“, shrimp utilize hemocyanin as the oxygen-carrying pigment which has an analogous role to hemoglobin.

It has been estimated that, on a fresh-weight basis, approximately 40% of the whole-body copper load in shrimp is found in hemocyanin. Thereby indicating the tremendous significance of meeting copper requirements in shrimp.

Interesting fact: According to some researchers, under different physiological conditions, shrimp can regulate their body copper concentration, which is required for hemocyanin synthesis.

Dwarf Shrimp and Copper Supplementation

There are only two ways for shrimp to obtain copper. They can get it from ambient water or diets. Nevertheless, studies also showed that copper in the rearing water alone cannot meet the requirements. Therefore, dietary copper supplementation is essential for shrimp to meet the need for optimal growth, tissue mineralization, and reproduction.

Biologists distinguish inorganic sources (forms of copper) and organic sources (forms of copper). The organic sources are more stable in the digestive tract and less prone to interactions and antagonisms as they are bound to organic molecules and less accessible to interaction and binding.

Some studies have proved that dietary copper has a vital role in the innate immune response in shrimp. While chemical forms of copper affect its absorption and utilization. 

Copper concentration and Dwarf Shrimp

Now I have come to the most important part. What is the dangerous level of copper to the dwarf shrimp? Is the dangerous level the same for all dwarf shrimp?

If you search it on Google, the only good link will be to the “Theaquariumwiki”. It states that the dangerous level of copper for:

• shrimps is 0.03 mg/l (mg per litre).
• algae and bacteria is 0.08 mg/l.
• some fish, snails, and plants are 0.10 mg/l.

Unfortunately, there is no information and references for the source of this data.

Note: If we look at Seachem Cupramine, it says “most fish tolerate Cupramine to 0.8 mg/l, it is not advisable to exceed 0.6 mg/l”. As we can see, we already have some significant differences in numbers.

Frankly saying, I spent several days trying to find official studies and reports. Out of a dozen studies, there is only one, which gives us the direct answer we need. The study is called “Histological Changes in the Gills of Two Freshwater Prawn Species Exposed to Copper Sulphate” (January 1979).

According to the experiment, shrimp of the approximately same size (Macrobrachium ~6 cm and Caridina ~2.5 cm) were exposed both to copper sulphate solutions. The results revealed that copper is highly toxic to both species of shrimp. Hundred percent mortality occurs in 0.5 mg/l concentration. The 48 hr LC50 value comes around 0.3 mg/l. Spontaneous movement and irritated behavior of shrimp were noted at higher concentrations of copper.

Note: LC50 is the lethal concentration required to kill 50% of the shrimp population.

Well, this number is 10 times higher compared to “Theaquariumwiki”!
Can it be a mistake?

Copper Sulphate and Aquatic Inhabitants

As I have already said, I have read many studies and reports, and if we look at some other results it can let us better understand the problem. Let me give you some other examples of how copper affects aquatic inhabitants.

Australian Glass Shrimp (Paratya australiensis) showed less tolerance to copper. Its dangerous level of copper coincides with “Theaquariumwiki” (0.03 mg per liter).

Note: In general, the mortality of tested aquatic species is greatest under conditions of low water hardness, starvation, high water temperatures, and among early developmental stages.

Warning:

As we can see, all shrimp species have different susceptibility to copper. Even within the same species, the tolerance can be different because of the size and molting stage (see later). Unless we get more studies regarding specific species (Neocaridna and Caridina shrimp), it is not possible to determine the real threat of copper to dwarf shrimp.

Therefore, we still have to play very safely. However, this data gives some hope to believe that dwarf shrimp can be tougher than we initially thought.

Caution should be exercised against water source contamination and exposure to fertilizers in shrimp tanks as well. 

Copper Intoxication signs and behavior of Dwarf Shrimp

Peculiar behavioral alterations have been observed almost in all shrimp species after exposure to copper sulphate during the copper toxicity tests.

1. At first, shrimp quickly respond in the form of increased movement.
2. They can also start scrapping of body parts.
3. The increased surface movements can be observed in the first few hours of the exposure. Although, it usually normalizes within 24hr of exposure, thereafter animals settle on the bottom of the aquarium.
4. The mucus production on the gills starts after 24hr of exposure and is maximum after 96hr (covering almost all the body parts). Biologists believe that the mucous secretion may be an important factor to combat the toxic effects of the copper solution.
5. Some shrimp species have the blackening of the undersurface of the carapace (just above the gill region).
6. After 72 hours shrimp become sluggish with decreased scrapping and respond feebly to gentle paddling.
7. After 96 hours reduction in all activities up to maximum lethargicness. At this point, there are certain alterations in muscle fibers.

Accumulation and Storage of Copper in tissues of Dwarf Shrimp

For many freshwater shrimp and crayfish, whole-body and individual tissue loads of copper increase at rates that are approximately proportional to the copper concentration in the water and to the duration of exposure (often over many months). This indicates that excretion rates are very low relative to uptake rates.

For example, copper, which was steadily accumulated by freshwater crayfish, over a period of 8 weeks, was lost again over a similar time course in clean water. Biologists believe that the haemolymph (the blood) acts as a transport system for copper in these crustaceans but is not a site for accumulation.

Shrimp, Copper, and Molting

Protein, hemocyanin, and copper concentrations in the hemolymph of shrimp fall steeply at the molt. The decrease often starts just before molting, reaching a minimum in post-molt stages, and is followed by a gradual recovery through the inter-molt and pre-molt stages.

For example, Australian Glass Shrimp (Paratya australiensis) had a decreased molt period of 23 days (range 20-27 days) vs. 25 days (18-36 days) in 0.015 mg/l.

Another example, shrimp Litopenaeus vannamei:
– 0.05 mg/l (safe level) – accelerated the molting process.
– 0.1 mg/l (safe level) – accelerated both the molting and reproduction cycle.

These results provide strong evidence that a trace amount of copper is an essential part for both molting and reproduction in shrimp. In addition, recent biochemical studies have certainly shown that changes in hemocyanin synthesis are correlated with particular stages of the molt cycles.

However, there are still many gaps in the overall picture of the metabolism of copper and hemocyanin in shrimp.

Copper and pH in a Tank

In alkaline water (high pH), copper ions bind to calcium carbonate (KH). Therefore, the amount of free copper ions in the water decreases. However, if the pH drops, the poisonous copper ions will be released again.

This is extremely important, because a safe concentration of copper at higher pH may become a lethal dose at a lower pH.
At low pH levels, the water is poorly buffered and copper can become very toxic.

Fertilizers, Copper, and Dwarf shrimp

A lot of shrimp tanks also have plants. Therefore, aquarists often ask, can they use fertilizers? Which ones are shrimp safe? The problem is that almost all of them contain copper and most shrimp breeders are paranoids when it comes to the safety of their shrimp colony. Especially when they hear the word Copper.

I know for sure, that the absolute majority of professional shrimp keepers never use plant fertilizers in their shrimp tanks. Shrimp are too sensitive and nobody wants to take any risk (even the smallest).

I have looked through the most popular plant fertilizers and picked the safest for the shrimp. Although, they do contain copper, the amount of it is minuscule.  This is the list.

1.  Seachem Flourish

Seachem Flourish contains a rich assortment of important micro elements, trace elements, and other nutrients. These include calcium, magnesium, iron, copper (0.0001%), and other important elements to aquatic plants and shrimp as well.

According to Seachem, Flourish is safe for invertebrates such as shrimp. I quote from the official site “Yes, Flourish® is safe to use with shrimp. It is true that in large amounts, copper can be toxic to aquatic animals and invertebrates like shrimp and snails can be particularly sensitive. However, copper is needed in trace amounts by both plants and animals, including shrimp, which is why we include it in Flourish, Flourish® Trace, and our other Trace products. The amount of copper in Flourish® is so small that you would have massively overdose before you would begin to approach an amount of copper that is toxic to even the most sensitive animals. There is usually much more copper in tap water than there is in Flourish”.

2. Dennerle series of fertilizers

Dennerle is a world-known German company producing aquarium and pond supplies. They are working with Shrimp King (Chris Lukhaup) himself. Dennerle has a wide variety of pretty much everything you need, including (as they say) shrimp safe fertilizers.

Quote “We often hear that fertilizers are bad for shrimps… But when these products are used correctly (right product at the right dose), they are not dangerous at all! All the Dennerle fertilizers are shrimp safe. Even the iron, with our E15 FerActiv!“

This is what they advise for the shrimp tanks: Dennerle E15, Dennerle V30 Complete, Dennerle A1 Daily, Dennerle S7 Vitamix.

3. JBL series of fertilizers

JBL is another German company, which supplies 60 countries worldwide with a product range of over 1000 products.

According to them, I quote from the official site “The concentration in JBL Ferropol, JBL Ferropol 24 and JBL ProScape Fe +Microelements is so designed that all trace elements are available in the required quantities. Not even multiple overdosing of the fertilizers can lead to consequences with shrimps and other decapods”. 

4. Biovert Plant Fertilizer

Biovert Plant Fertilizer provides all the trace elements you need to ensure healthy plant growth.

But the most important for us is that it is shrimp safe. Do BioTrace and BioVert contain copper? Is this copper could be a problem for invertebrates like shrimps?

I quote “The quantity of copper in these products is low and below the dose harmful for shrimps. The products can be used without fear and under conditions noticed on the packaging”.

5. Sera florena

According to them, it is well tolerated by all invertebrates. However, they do not tell us how much copper this fertilizer has.

Sera Florena .

How to test your Tank for Copper

The main problem here is that many common copper test kits are not sufficiently sensitive. They can often show concentrations that are already deadly for the shrimp. That is why we need to choose test kits, which can work with small concentrations.

We have two main favorites here.

1.  API Copper Test KIT (detects copper levels from 0-4 ppm)

• Fill a clean test tube with 5 ml of water to be tested (to the line on the tube).
• Add 10 drops of Copper Test Solution, holding dropper bottle upside down in a completely vertical position to assure uniformity of drops.
• Cap the test tube and shake for 5 seconds.
• Wait 1 minute for the color to develop.
• Remove the cap. Hold the test tube upright over the white area on the color card and view the color of the solution by looking down from above. The closest match indicates the ppm (mg/L) of copper in the water sample. Even a very faint color indicates the presence of copper. Rinse the test tube with clean water after use.

API Copper Test KIT.

2.   Seachem MultiTest™ Copper (Range Measures between 0–0.80 mg/L copper)

Copper kits are usually of two types: compleximetric or titration based. Some kits measure only ionic copper and others measure both ionic and chelated copper. This kit uses a highly sensitive catalytic compleximetric based procedure to measure all types of copper to less than 0.01 mg/L in marine or freshwater. MultiTest™ Copper performs over 75 tests and contains a reference sample for validation.

1. Fill sample pipette to base of the bulb and dispense to a test cavity of the test plate. Repeat, adding to the same cavity.
2. Add 2 drops of Copper Reagent 2.
3. Insert the dry Stir rod into the Copper Reagent 1 container to coat the rod with a very light dusting of Copper Reagent 1. Gently tap the rod against the side of the container to shake off excess Copper Reagent 1. Dip Stir rod with Copper Reagent 1 in the test cavity and stir briefly.
4. Compare color with color chart within 20 to 30 seconds after stirring. If testing chelated copper, read after 15 to 25 minutes. (Cupramine™ is not chelated.)
5. Promptly dispose of completed test solutions by rinsing the test cavity under running water. If the test plate becomes stained, soak or clean with a dilute bleach cleaner, then rinse well.