Avoiding aggression with my wrasse.
When I introduce fish into my wrasse collection the thing I am trying to avoid is aggression. There are a number of interesting articles about wrasse compatibility within genera, ie Fairy wrasse or Leopard wrasse, but I am mixing fish from several different genera. I need to try and avoid the long term problems that behavioural stress caused by aggression from tank mates can have on my fish.
I believe that fish in general tend not to be indiscriminately aggressive but are aggressive for a reason. Aggression is a high energy activity for the fish which should be avoided if possible. My experience is that fish tend to display antagonism towards members of their own species and other fishes that compete with them for territory, shelter, food or mates. A number of studies suggest fish recognize competitors by their general body shape, colour and behaviour.
There are a number of factors which could determine how individual fish react to other fish within the aquarium. Firstly some species are just more aggressive in their reactions than others. (my pair of tomato clowns!) Fish which have been living in the tank for a period of time maybe more likely to show aggression towards a newly introduced fish. Aggression is also more likely if a tank is overstocked as space, shelter and possible food might be in short supply. Hopefully I will be able to minimise aggression from these factors.
I believe that fish in general tend not to be indiscriminately aggressive but are aggressive for a reason. Aggression is a high energy activity for the fish which should be avoided if possible. My experience is that fish tend to display antagonism towards members of their own species and other fishes that compete with them for territory, shelter, food or mates. A number of studies suggest fish recognize competitors by their general body shape, colour and behaviour.
There are a number of factors which could determine how individual fish react to other fish within the aquarium. Firstly some species are just more aggressive in their reactions than others. (my pair of tomato clowns!) Fish which have been living in the tank for a period of time maybe more likely to show aggression towards a newly introduced fish. Aggression is also more likely if a tank is overstocked as space, shelter and possible food might be in short supply. Hopefully I will be able to minimise aggression from these factors.
So, as I have already stated fish tend to show varying degrees of aggression to fish they recognise as competitors in some way. Several studies have shown the most important factor is body shape. Fish tend to display more aggression towards species with similar body shapes. Body shape can, to some degree, be an indicator of diet. The majority of herbivores are deeper-bodied and laterally compressed, while most predators are more elongate. Therefore, it makes sense for a fish to chase away species with the same form, because they probably also have a similar diet and will compete for food.
Colour has also been shown to be an important recognition factor. A study carried out on captive butterfly fishes indicated that species with similar colour patterns were more aggressive towards one another than they were to those that had different colours and patterns. Maybe the very distinct and bright colours of terminal males in most wrasse genera is a signal to other males to stay away from their harem of females. A number of fish can also show aggression to fish from different genera if they have a similar colour pattern. Something to be aware of when looking at my wrasse collection.
Colour has also been shown to be an important recognition factor. A study carried out on captive butterfly fishes indicated that species with similar colour patterns were more aggressive towards one another than they were to those that had different colours and patterns. Maybe the very distinct and bright colours of terminal males in most wrasse genera is a signal to other males to stay away from their harem of females. A number of fish can also show aggression to fish from different genera if they have a similar colour pattern. Something to be aware of when looking at my wrasse collection.
Another factor to consider, the feeding behaviour of a species can make it susceptible to some form of aggression. In my wrasse based reef tank, this and competition for shelter could be a real issue. Fairy and Flasher wrasse are both planktivores whilst my Halichoeres and Magropharyngodon wrasse all feed from the rocks or sand bed. They are also similar in their sleeping habits. The planktivores need caves or nooks and crannies to sleep in whilst my other wrasse are 'sand sleepers'
I have read a couple of papers about how a complex or 'enriched' environment can help to dampen aggression within the reef that seemed to make sense. Hopefully the rockscape, corals sand bed etc in my reef will offer my wrasse the environment they need.
When introducing new fish to the collection I am following the advice of Hunter Hammond in his excellent article All about reef Safe Wrasses in Aquaria (2016) in which he advocates the use of an acclimatisation box to allow the existing wrasse and the new wrasse to get to know each other and work out some sort of social structure without having to go through some actual aggression in the tank.
I have now used this box on several occasions very successfully. I have documented one introduction on my blog page
I have read a couple of papers about how a complex or 'enriched' environment can help to dampen aggression within the reef that seemed to make sense. Hopefully the rockscape, corals sand bed etc in my reef will offer my wrasse the environment they need.
When introducing new fish to the collection I am following the advice of Hunter Hammond in his excellent article All about reef Safe Wrasses in Aquaria (2016) in which he advocates the use of an acclimatisation box to allow the existing wrasse and the new wrasse to get to know each other and work out some sort of social structure without having to go through some actual aggression in the tank.
I have now used this box on several occasions very successfully. I have documented one introduction on my blog page
Hopefully keeping the fish well fed and feeding in an appropriate way will also minimise aggression within my little collection.
Finally the choice of fish. Haliochoeres are all of a similar shape so I will need to think carefully about the different species in order to make sure the colours and patterns are not too similar. I thought I had made a mistake when introducing a juvenile Halichoeres melanurus as the much larger H. timorensis took an instant dislike. It was not until both fish were in the tank that I realised the basic similarity in colouration. Fortunately both fish now know their respective places and live peacefully together. Currently my little wrasse community is living peacefully together with no overt aggression, just the odd little display to act as a reminder! It is interesting to see all of my wrasse raise their fins in display to each other.
One thing I will bear in mind...Do not introduce terminal males into the little reef!
The Acclimation Box: Can This Thing Really Work? Hunter Hammond (2015)
Socially Acclimating Fishes Austin Lefevre (2016)
Updated 29.10.20
Finally the choice of fish. Haliochoeres are all of a similar shape so I will need to think carefully about the different species in order to make sure the colours and patterns are not too similar. I thought I had made a mistake when introducing a juvenile Halichoeres melanurus as the much larger H. timorensis took an instant dislike. It was not until both fish were in the tank that I realised the basic similarity in colouration. Fortunately both fish now know their respective places and live peacefully together. Currently my little wrasse community is living peacefully together with no overt aggression, just the odd little display to act as a reminder! It is interesting to see all of my wrasse raise their fins in display to each other.
One thing I will bear in mind...Do not introduce terminal males into the little reef!
The Acclimation Box: Can This Thing Really Work? Hunter Hammond (2015)
Socially Acclimating Fishes Austin Lefevre (2016)
Updated 29.10.20