Comparison of Different Biofilter Media During Biological Bed Maturation Using Common Carp as a Biogen Donor
Round 1
Reviewer 1 Report
The manuscript “Comparison of Different Biofilter Media During Biological Bed Maturation Using Common Carp as A Biogen Donor” describes interestingly the changes in the nitrogen compound composition in recirculating aquaculture systems. The experiments were conducted in a scale that represents real applications and the nitrogen compounds have been analyses systematically and concentration profiles are nicely presented. However, the purpose of the study is not clearly determined, the obtained results are discussed very non-systematically, and the conclusions barely relate to the discussion.
The title suggests that the study focuses on comparing different biofilter materials and on maturation of the biological filters, but neither of these topics are discussed in the introduction. The authors should clarify, why there is a need to find alternative fillings and what are the characteristics that are required as well as what is considered a mature biological bed and what factors affect the maturation. The last paragraph should also be modified to clearly state the aim of the study.
The results section contains a lot of repeating sentences and thus the manuscript is not fluent to read. The authors should consider presenting more of the data in tables. What additional information do the regression equations provide?
The discussion section nicely compares the obtained results to previous studies, but factors compared are very broad and the comparison is not done consistently. The authors should also focus more on their own data: what were the reasons for the differences in the results obtain in this study? Which filling was performing best and why? What could have been the causes for poorer performance of different materials?
More detailed comments are below:
Line 45: The intermediate compound should be nitrite, not nitrate Line 46: What is meant by nitroso- and nitro-nitrification bacteria? Please clarify. Line 68: The first sentences of the paragraph seem to be out of place Line 74: Which factors the authors are referring to? Line 91: Does tap water refer to the water used to fill the tank? Figure 1,2 and 3: Consider combining the pictures to a single figure (A, B and C) Line 151: Why sodium chloride was added on this specific time? Lines 199 – 227: For example here the sentence structure is very repetitive. Consider presenting this data in tables. Line 251: Please state more clearly, which were the conditions for CFsf, how did it differ from other experiments and why it was used as a control Table 1: Please explain what do the letters a, b, c and d stand for Line 374: Explain denitrification here or already in the introduction. Consider also mentioning in the discussion, what could have been the reason for nitrate concentration to decrease in the end of the experiment Line 379: What do the authors mean by one time top-up? If water was added to the tanks during the experiment, that should be mentioned in the materials and methods. Line 462: Vaccination is not the correct term in this contextAuthor Response
All comments of the reviewer have been taken into account. Detailed answers are presented in the attached file.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors
The article addresses important issues related to the functioning of RAS. This paper is relatively well constructed and written. Extending the analysis by the quality of water draining from the rearing tank would allow a better comparison of filters. Please think over the combination of the research results and discussion chapters. Descriptions of results for some indicators is quite short and repeated in the discussion chapter. Maybe it would be better to comment on it on a regular basis.
Line 10; 53; 80, 114 etc. - spaces
Line 23, 95, 96, 379 – “L” or “dm3”, please unify the units record and adapt to the editor's requirements
Line 68-71; 81-83; 113; 140-144; 150; 411-413 – font type
Line 79-80 and 90-91 – can we speak about testing the functioning of filters in conditions of variable load, since its size was not determined (water quality after the filter was analyzed).
Line 101 – should be “m2”
Line 112-113 – I propose to explain on what basis the filter volume
was adopted?
Line 148 – is it about initial daily feed dose? which means „daily biomass”?
Line 150 – was the initial daily feed dose set at 3% of the initial fish biomass? does it give 20.9 g?
Line 151-152 – please explain the purpose of sodium chloride dosage
Line 152 – should be „N-N02”
Line 155 – was water quality determined at other points of the tested RAS, e.g. inflow to the biological filter, which would allow determination of the
homogeneity of conditions, load filters and efficiency. Taking these parameters into account would allow a more comprehensive comparison of biological filters
180-187 – for what purpose fish biomass and body length measurements were carried out at the end of the experiment, whether it had an impact on the interpretation of the results presented in the article and inference?.
Fig. 6-11 – I suggest you think about another way of presenting the results in graphs - in this form they are difficult to read.
Line 265 – please explain why the scale and period of increase of nitrogen
compounds concentration in the restarted system were lower compared to other systems?
Line 287 – shlould be “5.780 mg N-NO2/dm3”
Line 379 – whether it was a supplement or a water change, when and at what point in the system the procedure was performed, what effect did it have on the concentration of analyzed nitrogen compounds and for what period
Line 447 – should be „Karpiński at al. [53]”
Line 460 – should be “Kuhn et al. [45]”
Line 525-672 – position numbering
Author Response
All comments of the reviewer have been taken into account. Detailed answers are presented in the attached file.
Author Response File: Author Response.docx
Reviewer 3 Report
Dear Authors
We consider that the subject discussed in the paper that has been sent to us for review it is interesting not only from the point of view of assessing the potential impact associated with transformations of nitrogen compounds on fish production, but also in terms of the environmental sustainability of the sector. In fact, by maintaining the quality of recirculating water in fish ponds for a longer period, also contributing to the preservation and maintenance of an increasingly scarce resource. However, we consider that the article could be improved. In the introduction section we consider that it would be interesting to further research on the role of fillers in the dynamics of nitrogen compounds. Paragraph 2 of that section would also benefit from a clearer description. The material and methods section could also be improved as its description makes us unclear. The results would benefit from further discussion, especially it would be interesting to discuss the characteristics of the different fill media and their potential effect on tank environmental conditions and on the dynamics of nitrogen compounds. Indeed, from the results and discussion presented it is not clear which factors influenced the nitrogen transformations that were observed. In the results section it would be important that they always follow the same methodology of analysis of the results. In fact, we consider that the subchapters (3.1.2.1 ... and 3.2.2.1 ...) created at the level of analysis of nitrite nitrogen results only confuse the reader. The conclusions should be more objective in terms of the results they have obtained.
We believe that your paper is very interesting, but it will have to be improved
Best Regards,
Author Response
All comments of the reviewer have been taken into account. Detailed answers are presented in the attached file.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The readability of the manuscript has improved significantly due to the reordering of the data in tables. The authors have addressed most of the comments, but for some of the comments it is not clear what changes the authors have made, if any, and for some comments the explanation is provided in the cover letter, but not in the manuscript. For comments A, B and D, for example, I could not find related corrections from the manuscript, despite the very vague answer “It was corrected due to Reviewer suggestion”. The authors should point out more specifically the corrections made.
Line 50: The authors should explain shortly also in the manuscript the metabolic functions of the Nitroso- and Nitro-nitrification bacteria
Line 82: Mentioning some examples of the factors would be beneficial
Line 173: The reason for the addition of sodium chloride should be explained in the manuscript in more detail than in the reply. Why the addition of sodium chloride helps to prevent the nitrite poisoning?
Table 4: The caption is not fully in English.
Table 5: What do the letters a, b c and d stand for? The columns are also distorted.
Author Response
The all Reviewer commenct are accepted by the authors and corrected. The detailed ansewer are present in addiotional file.
Author Response File: Author Response.docx
