On the Trail of (Trace)elements in feed

18.09.2018

 

Often the question arises, which elements are inserted into the aquarium with popular feed. It is interesting to see if feed will cover (partially) the trace element need of the aquarium, or if feeding can lead to critical enrichment.

We not “only” use our laboratory to analyze your seawater samples, but also want to answer interesting questions, and gain new insights for our hobby.

 

 

In order to examine the (trace) elements in popular feed, we quickly dissolved the feed in concentrated acid, diluted them with ultrapure water and analyzed them by ICP-OES. We will share and discuss the results with you here

We have selected 3 types of dry food: "garlic" pellets, spirulina flakes and "colorful" flakes, as well as four frozen food types: artemia, krill, mysis and lobster eggs.

 

At this point, it should be mentioned that only one sample of each feed was analyzed. In order to obtain a more holistic picture, several batches of the respective feed would have to be tested and the values averaged. However, we believe that this pilot study provides valuable information on the trace element content of the respective feed. The values of dry and frozen food are only partially comparable with each other, since frozen food contains a larger amount of moisture.

But now to the results, we look at each element, and discuss succinctly whether the reading is relevant for aquaristics.

 

Let's start with barium, on the left in the diagram are the three dry food types, on the right the frozen food sorts. The unit is μg (micrograms) per gram of feed. So if about 1 g of "garlic" pellet is fed in an aquarium of 100 l volume, about 2 μg barium/100 l = 0.02 μg/l barium will enter the water.

The barium content varies between the feed types, but it is generally very low. Even with mysis (the feed with the highest barium content) only insignificant amounts are introduced into the aquarium.

Strontium is also entered only in very small amounts with the feed, therefore the strontium need must be fulfilled by additional supply (by means of a supply system, e.g.: Oceamo DUO, or through specific individual doses).

Aluminum is mainly known as a pollutant because it has no known biological function. Values above 100 μg/l can occasionally cause problems, especially effects on soft corals are being registered. In case of the examined feed types, the "colorful” flake food stands out due to its high aluminum content of 1150 μg/g. With a feeding of 1 g/100l (a fairly high amount), 11.5 μg/l of aluminum is introduced per feeding, which can definitely lead to undesired accumulation. The tested artemia have the second highest aluminum content of 111 μg/g.

Iron is an important trace element. All dry foods, lobster eggs, and brine shrimp bring in significant (but by no means critical) amounts of iron, which is why feeding will probably cover the iron needs well. The examined krill and mysis contained significantly less iron.

​Copper, an important trace element as well (causing often problems in high concentrations) is detectable in all types of feed. In particular, the examined Lobster eggs had a high copper content. - Exclusively feeding these crayfish eggs may cause an increase in the copper content in the tank, we definitely recommend varying the feed used, in order to avoid unilateral load.Copper, an important trace element as well (causing often problems in high concentrations) is detectable in all types of feed. In particular, the examined Lobster eggs had a high copper content. - Exclusively feeding these crayfish eggs may cause an increase in the copper content in the tank, we definitely recommend varying the feed used, in order to avoid unilateral load.

The zinc content in dry food is significantly higher than in frozen food (except spirulina), and considerable amounts are introduced (mainly from pellets). However, toxic accumulation is extremely unlikely.

Vanadium is detectable only in minimal amounts in the analyzed feed, the feeding does not contribute significantly to the vanadium supply of an aquarium.

Likewise, nickel, molybdenum and chromium. Although these elements are detectable in most types of food, a significant admission into the aquarium does not occur.

​The important trace element manganese is entered by all feed types, whereby krill contains the least manganese. High manganese levels are found in pellet and flake food, as well as Artemia.

But not only metals are interesting in aquaristics, but also phosphorus, for example, which occurs (mostly organically bound) in all types of food. - Thus, food is also the main source of phosphate in the aquarium. It is interesting that the phosphorus content differs significantly between the types of feed studied, but see for yourself:

Striking is the very high phosphorus content in the investigated pellet feed: almost 18000 μg/g, ie 18 mg/g or even 1.8% of the feed weight. Spirulina has the lowest phosphorus content in dry food, and the frozen feed all have a similar phosphorus content.

 

We have also converted the phosphorus content into the potential increase in phosphate value when 1 g of each feed is fed to 100 liters of aquarium water (assuming that all phosphorus ends up as phosphate in the water. In reality, part of the phosphorus is also used by the fish, and therefore contributes nothing to the phosphate content in the water, the data should therefore be considered as an approximation):

If 1 g of the pellet feed is fed per 100 l of water volume, theoretically the phosphate value can rise to just under 0.6 mg/l. The other types of food also provide a significant intake of phosphate (which is also needed as an important nutrient for the aquarium). If you have problems with high phosphate levels, you should avoid feeding pellets. (Even with high phosphate levels, it is important to ensure adequate feeding of the fish! - Spirulina, for example, contributes significantly lower amount of phosphate).

 

​We hope our little study was interesting for you! A discussion board is available on our forum on www.nanoriffe.de. And course, we are also available via e-mail!

Which feed types and elements are you particularly interested in? We look forward to your suggestions for FoodTrace Part 2!

 

Best regards,

Christoph and Kerstin

Your Oceamo Team