by , Nathan's Marine Aquarium Page

Introduction

G'day all interested in the plight of captive Mandarin Dragonets.

First of all, let me say thank you to all who sent in their responses, it was a great effort, and I was able to use 40 of the 47 responses that I received. Albert Thiel's list gets the prize for the most respondents. The 7 responses that I wasn't able to use were discarded because they were:

• only general responses and not direct answers to the questions in the survey
• were references to Mandarins that they had not personally kept
• were responses from LFS that did not have long-term experience with all the Mandarins that they were basing their data on

There were a number of questions that I immediately wished I had asked as soon as I started getting results of the survey back. Some respondents also suggested some questions too. They were:

• What sex was the Mandarin you kept?
• Does one sex seem to take more readily to prepared foods than the other.
• Do you know which region it was collected in?

I will now go through with a breakdown of what I was able to interpret from the data I received.

Introduction
General Health
Spawning Behaviour
Food Types
Breakdown of Individual Foods
Feeding Frequency
Algae
Tank Style
Competition for Food
Filtration
Tank Size
Live Rock
Live Rock per Gallon
Live Sand per Gallon
Mandarin Appearance at Purchase
Cause of Mortality
Conclusion

General Health

The good news is that 45% (17) of respondents believe that they're Mandarins generally thrive in their aquariums. 7.5% (3) said they didn't know due to only having had them a short time (between 2 and 7 months), although this didn't seem to stop 3 others with only similar lengths of experience saying that theirs were thriving 22.5% (10) were just hanging in there. The length of time that these Mandarins had been kept for and were still alive ranged between 4 and 24 months. Some of the respondents said that they suspected that their Mandarins would soon be going downhill due to the microfauna population starting to run out. 22.5% (10) were going downhill. Just about all of the respondents whose Mandarins were going downhill said it was due to the micro-fauna on their rock running out. The others that didn't mention food running out, didn't speculate at all on why they were going downhill.

Spawning Behaviour

Only 10% (4) respondents had had Mandarins go through spawning behaviour in their tanks but only two of them reported any resulting eggs on a regular basis. Of the two that pairs that regularly produced, one pair was described as apart during the day but together at night. The other pair was just described generally as paired up. This pair had spawned so frequently, that the female had died from exhaustion.

A third pair had produced eggs once and was also described as apart during the day but together at night.

The food that the pairs of Mandarins that went through the spawning ritual had access to are as follows:

1. Regular spawning, majority food: in tank, majority of nutrition: in tank.
   Extreme Enthusiasm: live mysid shrimp, copepods and rotifers
   Enthusiasm: na
   Reluctanly: live baby brine shrimp and dead bloodworms
   Very Reluctanly: live adult brine shrimp
   Ignored: frozen plankton, flake food, dead mysid and dead adult brine shrimp.
2. Regular spawning, majority of food: not stated, majority of nutrition: not stated.
   Extreme Enthusiasm: live adult brine shrimp, live mysid shrimp, copepods
   Enthusiasm: dead adult brine shrimp, live baby brine shrimp, amphipods
   Reluctantly: live bloodworms
   Very Reluctanly: Formula1, Formula 2, frozen seafood, flake food, pellets
   Ignored: n/a
3. Only one spawn witnessed, majority of food: added, majority of nutrition: 50/50.
   Extreme Enthusiasm: copepods
   Enthusiasm: gut-loaded brine shrimp
   Reluctanly: dead adult brine shrimp
   Very Reluctantly: n/a
   Ignored: n/a
4. Spawning behaviour but no spawn, majority of food: "definitely from what is available in the tank", majority of nutrition: "definitely from what is available in the tank".
   Has only witnessed female eating "brine shrimp,... copepods and other small, unidentified critters that live in [the] rock". It appears therefore that the male must also be eating the same stuff but the respondent had not seen this occur.

20% (8) had reported keeping more than 1 Mandarin at a time. Out of these 50% had behaved favourably toward each other and stayed together during the day. Out of the other 50%, 2 "pairs" had had one kill the other and the other 2 "pairs" couldn't care less about each other.

It is interesting to note that all but one of these pairings were considered to be thriving. The odd one was considered to be going downhill but this was one of the ones that was going through the spawning behaviour but had produced no eggs.

Food Types

A complete breakdown of the numbers of foods taken by Mandarins and their corresponding enthusiasm to them is below but I have created a quick reference list here.

It is ordered in two ways. The first listing orders the percentage of Mandarins that took a particular food out of all the Mandarins that were offered that food. The second list orders the percentage of Mandarins that took a particular food with any enthusiasm (ie, scored a 1 or a 2 in the survey) out of all the Mandarins that were offered that food. Personally, I prefer the second list because it is listed by enthusiasm which means that Mandarins are most likely to eat these foods. The first list just shows a range of foods that Mandarins may eat, but not with how much enthusiasm they are likely to eat it.

After the percentage for each food, I have provided the number of Mandarins that were offered that food in order to give an idea of how relevant the percentages are. Obviously, the higher the number of Mandarins that were offered the food, the more likely the percentage derived is accurate for Mandarins in general.

List 1 - Percentage of mandarins that took a food out of all mandarins offered that food

List 2 - Percentage of mandarins that took a food ENTHUSIASTICALLY out of all mandarins offered that food

Breakdown of individual foods

Copepods

85% of the respondents had reported their Mandarins having access to Copepods with results as follows:

All of the respondents that said that their Mandarins got most of their nutrition from within the tank (75%) also had access to Copepods. 100% of Mandarins with access to Copepods took them enthusiastically.

Live Adult Brine Shrimp

75% of the respondents had reported their Mandarins having access to live adult Brine shrimp with results as follows:

So, it appears that 46.6% of Mandarins offered live adult Brine shrimp had taken them with any enthusiasm. 80% had taken them when offered though.

It is interesting to note that out of all of the brine shrimp taking Mandarins, all but 7 were considered to get most of their nutrition and food from what is available in the aquarium. 2 of the 7 were "don't know"s.

Dead Adult Brine Shrimp

29.63% of Mandarins offered dead adult Brine shrimp would take them with any enthusiasm. 59.25% had taken them when available, though.

2 of the Mandarins that had taken dead adult Brine with any enthusiasm and one that had taken them reluctantly, had not taken live adult Brine at all. This brings the total percentage of Mandarins taking any form of adult brine shrimp to 67.5% but with only 40% taking them with any enthusiasm.

Live Brine Shrimp Nauplii

76.47% of respondents Mandarins took live Brine shrimp nauplii although only 52.94% took them with any enthusiasm.

Dead Brine Shrimp Nauplii

Live Bloodworms

100% offered were taken but none enthusiastically.

Dead Bloodworms

44.44% offered were taken but only 22.22% enthusiastically.

Live Blackworms

80% offered were taken but only 40% enthusiastically.

Dead Blackworms

Live Daphnia

75% offered were taken but only 25% enthusiastically.

Dead Daphnia

60% offered were taken but none enthusiastically.

Live Mysid Shrimp

75% offered were taken AND enthusiastically.

Dead Mysid Shrimp

60% offered were taken, but only 20% enthusiastically.

Amphipods

94.11% offered were taken AND enthusiastically.

Rotifers

90% offered were taken, but only 70% enthusiastically.

"Formula 1" Style Food

50% offered was taken but NONE enthusiastically.

"Formula 2" Style Food

57.14% offered was taken, but NONE enthusiastically.

Frozen Seafood

35.71% offered were taken, but NONE enthusiastically.

Flake Food

18.51% offered were taken but NONE enthusiastically.

Pellet Food

14.28% offered were taken AND enthusiastically.

Freeze Dried Tubifex

50% offered were taken AND enthusiastically.

Live Tubifex

Beef Heart

Gut Loaded Brine Shrimp

100% offered taken AND with enthusiasm.

Frozen Shrimp

100% offered were taken but NONE enthusiastically

Mosquito Larvae

100% offered were taken AND enthusiastically.

Frozen Plankton

Prawn Eggs

Feeding Frequency

This didn't really show any trends except to say that all except one person whose Mandarin had access to Copepods was not actually providing them but just relying on what was on the live rock in the tank. Amphipods were the same.

Rotifers were interesting as 50% of those respondents whose Mandarins had access to them said that rotifers were always available in their aquarium. The other 50% supplied them.

Algae

45% of respondents had some algae in their tanks. These were described as:

This is a total of 7 thriving (38.8%), 4 hanging in there (22.22%) and 5 going downhill (27.77%). This compares with the general health of the respondents Mandarins at 17 thriving (45%), 10 hanging in there (22.5%) and 10 going downhill (22.5%).

As you can see, there is not a lot of difference, but if anything, the picture looks worse for the Mandarin aquariums WITH algae although the ones that responded with Macro-algae look reasonable but the numbers are too small to really make anything of.

Tank Style

All bar 3 of the respondents had reef tanks. This is to be expected considering that most of the forums that the survey went to were mainly for reef hobbyists. The 3 that didn't have a reef, were fish only. 2 had had Mandarins go downhill and the other had had them thrive.

Competition for food

This was an exact 50/50 split between competition for food and no competition. General health compared to competition was as follows:

• 
  No competition

  Thrive	13 (65%)
  Hang in there	5 (25%)
  Downhill	2 (10%)

• 
  With competition

  Thrive	7 (35%)
  Hang in there	4 (20%)
  Downhill	7 (35%)
  Unknown	2 (10%)

It appears that having no competition plays a big part in Mandarins being able to stay alive in the aquarium.

Filtration

Filtration did not seem to play any part in the health of the Mandarins.

Tank Size

I have broken up the tank sizes into what appears to be some obvious boundaries.

• 
  20 - 29 gal

  Hang in there	1
  Downhill	2

• 
  30 gal

  Hang in there	3
  Downhill	1

• 
  45 - 45 gal

  Thrive	3
  Hang in there	1
  Downhill	2

• 
  55 - 58 gal

  Thrive	4
  Hang in there	3
  Downhill	2

• 
  75 - 300 gal

  Thrive	13
  Downhill	2 (75 and 100 gal)

Obviously, this shows that the larger the tank the more likely it is for the Mandarin to survive. Anything larger than a 75 G, you can be fairly confident that the Mandarin will thrive but anything less than a 40 G and you are guaranteeing your Mandarin a miserable existence.

Live Rock

It appears that there is a threshold amount of live rock that a Mandarin can be sustained upon. That level is around 100 lbs. Some Mandarins will still survive below this level, but it appears that they are far more successful with this amount or more.

• 
  15 - 90 lbs of live rock

  Thrive	7 (2 x 45, 3 x 55, 80 and 90 gal)
  Hang in there	8 (25, 3 x 30, 40, 2 x 55 and 90 gal)
  Downhill	7 (20, 30, 2 x 40, 55, 75 and 100 gal)
  Undetermined	1 (90 gal)

• 
  100 - 300 lbs of live rock

  Thrive	9 (55, 70, 90, 4 x 100, 115, 120 and 300 gal)
  Hang in there	1 (55 gal)
  Downhill	1 (58 gal)

Live Rock Per Gallon

I thought it might also be important to give some information as to general health versus amount of rock. I have shown the sizes of the tanks for each health level.

• 
  0 lbs/gal

  Thrive	2 (45 and 100 gal)
  Hang in there	1 (29 gal)
  Downhill	1 (29 gal)

• 
  0.375 - 0.75 lbs/gal

  Thrive	1 (80 gal)
  Hang in there	2 (55 and 90 gal)
  Downhill	4 (20, 40, 75 and 100 gal)

• 
  0.778 - 1 lbs/gal

  Thrive	7 (2 x 45, 90, 120 and 125 gal)
  Hang in there	1 (30 gal)
  Downhill	1 (80 gal)
  Not stated	1 (80 gal)

• 
  1.091 - 1.5 lbs/gal

  Thrive	9 (3 x 55, 75, 90, 3 x 100 and 300 gal)
  Hang in there	3 (30, 40 and 55 gal)
  Downhill	2 (30 and 40 gal)

• 
  1.6 - 3 lbs/gal

  Thrive	3 (55, 100 and 115 gal)
  Hang in there	3 (25, 30 and 55 gal)
  Downhill	1 (58 gal)

It appears here that somewhere between 0.778 and 1.5 lbs/G is optimal with more rock than this appearing to be worse. The reason is obviously more to do with the size of the tank and the total volume of rock than the ratio.

Live Sand Per Gallon

Live sand does not seem to play as big a part in keeping Mandarins alive as live rock. This is probably understandable considering that Mandarins suck their food up and doing this on the substrate results in a mouthful of sand. I have shown the sizes of the tanks for each health level.

• 
  0 lbs/gal

  Thrive	7 (45, 75, 80, 2 x 90, 100 and 300 gal)
  Hang in there	5 (30, 40, 2 x 55 and 90 gal)
  Downhill	4 (29, 40, 55 and 58 gal)

• 
  0.2 - 1 lbs/gal

  Thrive	4 (2 x 55 and 2 x 100 gal)
  Hang in there	2 (25 and 55 gal)
  Downhill	5 (20, 30, 40, 75 and 100 gal)

• 
  1.04 - 1.83 lbs/gal

  Thrive	7 (2 x 45, 2 x 55, 100, 115 and 125 gal)
  Hang in there	2 (2 x 30 gal)
  Downhill	None

I think there is a slight trend toward the more sand the better for the smaller tanks, which does make some sense. Just about all the small tanks where the Mandarins were thriving had both large amounts of live sand and live rock.

Mandarin Appearance At Purchase

• 
  60% of Mandarins purchased were considered fat.

  Thrive	10
  Hang in there	6
  Downhill	7

• 
  22.5% were considered to have indented stomachs.

  Thrive	6
  Hang in there	1
  Downhill	2

• 
  10% were considered average

  Thrive	1
  Hang in there	2

• 
  7.5% made no comment.

These figures seemed strange to me and prompted me to compare what foods were eaten by the Mandarins with the indented stomachs compared to the fat Mandarins. I suspected that the Mandarins with the indented stomachs may have actually been so hungry that they would take a wider range of food than the fat Mandarins. As it turns out, the Mandarins with the indented stomachs are far "less" likely to take a wide range of food than the Mandarins with the fat stomachs. In fact, in just about all cases, the Mandarins with the indented stomachs would only tank what was on the live rock.

My next guess was that maybe the Mandarins with indented stomachs just happened to be kept in larger aquariums or with more live rock. This turns out to be the case. All but one of the indented Mandarins that thrived was kept in an aquarium 100 G or larger and all but two had more than 80 lbs of live rock.

I checked the fat Mandarins that thrived, and these included all the ones that had been able to thrive in the smaller tanks (55 - 75 G) with only 60 lbs of live rock or more (although two only had 35 lbs and were in 45 G tanks). All but two of the Mandarins that were "hanging in there" or going "downhill" were in smaller tank with less than 60 lbs of live rock (except for 2 cases that had larger tanks and more rock).

In my opinion, this shows either one of two things.

1. Fat Mandarins will adapt to smaller tanks with less live rock than those with indented stomachs.
2. OR... When kept in smaller tanks, fat Mandarins take a long time before they start going downhill.

I am hoping the former.

Cause Of Mortality

The overwhelming majority was starvation but a few were due to strange happening such as being eaten by an anemone. Thankfully, almost 25% had not experienced a Mandarin death. The numbers below will not add up to 40 as some people had given various reasons for death.

Conclusion

Well, that is about all there is to say. I think something very important that has come out of this is that probably the most important factor in determining if a Mandarin will stay alive or not is the amount of rock, the size of the tank and competition for food.

There are obviously some prepared foods that are more likely to be taken than others, but what seems to determine if a Mandarin will survive when bought with an indented stomach is still the amount of rock and the size of the tank as it appears that starving Mandarins will not just eat anything.