Aquarist - the Regulator
Myths in Fishkeeping II
Written by Thursday, 30 October 2008 00:00
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| Myths in Fishkeeping II |
| Page 2: Feeding Live or Frozen Food |
| Page 3: Notes |
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Feeding is an important part of fish keeping. “Myths” around feeding are plentiful. We will start with a really common one, namely that fish are “greedy” (= excessively desirous of food, esp. in large amounts, voracious). This is derived from the fact that fish will beg for food (i.e. come to the front of the tank every time they see their keeper). It is interesting that people who will tell you this will also throw at you the exact opposite: ‘remove any uneaten food from the tank’. What seems to us an obvious question, namely how come and there is uneaten food in the tank if the fish are indeed greedy, isn’t clearly as obvious to everyone. That is not surprising, given the fact that this is precisely how “myths” work: being taken as axioms, they are seldom questioned. Let us look at some myths related to feeding.
1. How many times a day do I feed?
2. Fish are greedy – too much food is not good for them.
We are all familiar with the moto “feed two or three times daily as much as your fish will consume in a few minutes”. As opposed to this, some claim that fish should be fed twice or three times a week. This, combined with another long standing myth in the hobby, namely that fish are greedy eaters and too much food is not good for them, often results in hobbyists feeding incorrectly.
We need to start this discussion by drawing a line between feeding and nourishing. We take feeding to mean providing food (i.e. edible matter) and nourishing to refer to the provision of materials essential for life and growth.
There is clearly a difference between feeding and nourishing and this regards both the quantity and the quality of the food available. Feeding is a natural activity consisting of three elements: (1) getting food which is pleasing to taste or smell (it is mainly smell that attracts fish to a particular type of food) and (2) getting a feeling of “fullness” (until this is achieved feeding continues) with the eventual aim of (3) extracting nourishment from the eaten food.
Food can be nourishing or not (in humans the latter is called junk food). Under the circumstances, nourishing can take place if we offer very small quantities of food packed with essential elements, vitamins, minerals etc. Feeding, on the other hand, as in (1) and (2) above, does not necessarily or cannot take place in this case. To get a clearer picture of this ask yourselves the question: How would you feel if someone put you, all of a sudden, on the astronauts’ diet? A-pill-a-day would be sufficient to cover your dietary needs, but would it be satisfactory – and would you consider yourselves well fed? Clearly not. No surprise that this holds true for the fish too. A natural grazer, who is used to consuming large amounts of vegetable matter daily, will clearly not be satisfied with a spirulina tablet, though it could well be the case that this tablet provides it with all the essential nutrients it would normally extract from 500 grams of food in nature. Under the circumstances, the manifestation of what is taken to be “greedy” behaviour, namely asking for more food when a fish has just been fed, doesn’t come as a surprise.
Fish manifest behaviour mistakenly taken as “greediness” for a number of reasons, in addition to the above. One of this is being fed at irregular intervals. Again, this is rather natural, emanating from their “insecurity” regarding the time at which the next meal will be offered. If the fish are not used to a routine, they will naturally try to eat as much as possible during one feeding session in order to ensure that they have enough supplies in case the next feeding session is far removed from the one that just took place. Another reason is the stage of growth they are in; younger fish, on the main, eat more than adult individuals. And so on.
Feeding the wrong type of food can also result in the manifestation of “greedy” behaviour in some species. As the fish cannot get the nutrients they need, they keep looking for food, regardless of how much they have consumed. This is related to both the type of food we offer fish and to the way in which fish (and all living organisms) metabolise their food intake.
Food consists of amino-acids. Vegetable and animal proteins contain amino-acids in different sequences, quantity etc. Thus one aminoacid may be very rare in vegetable protein but abundant in animal protein. If the organism is fed the wrong kind of food, it will have to spend a lot of time and energy to break the food down to its consistent aminoacids (catabolism) and then a lot of time and energy to compose these aminoacids to a form of energy which it can use (anabolism). This means that most of the energy from this food will go towards metabolising it - very little, if any, will be left for the organism to use for other activities such as movement, growth etc. (1)
Metabolism is the whole range of biochemical processes that occur within a living organism. There are two processes in metabolism,anabolism and catabolism (the build up and breakdown of substances, respectively). The term is commonly used to refer specifically to the breakdown of food and its transformation into energy. (2) Metabolism, feeding and growth in fish have been shown to depend on a number of environmental factors like temperature, photoperiod, oxygen concentration, existing bioload etc. (3)
Temperature is an easy one to identify. It is by no means the only water parameter that affects fish feeding behaviour and metabolism. In the first part of this discussion we referred to an experiment related to fish feeding routines and their outcomes in ponds and aquaria. In short, fish fed in aquaria could be induced to manifest nutritional deficiencies when put on a particular diet whereas fish living in more 'natural' environments (ponds) did not manifest the same deficiencies when put on the same diet. The reason was that in ponds fish had access to other edible matter (insects, algae etc) which clearly catered for the gap in the feeding regime provided by the researchers.
We feel there is more to it than that. Our own observations indicate that individuals belonging to the same species kept in waters with different parameters (primarily pH, KH, GH, salinity) show specific preference for particular, different between them, types of food. A prime example of this was a pair of L47 (Baryancistrus sp., Magnum pleco), which were brought up in Manchester and then moved to Athens. In Manchester the fish were fed, for over 4 years, fresh vegetables. The male in particular was extremely keen on potatos and courgette. Please take into account that both these fish manifested an active preference for these vegetables; they would ignore other food in favour of the particular veggies. When moved to Athens the fish refused, time and time again, to eat their favourite food - to the point that we eventually stopped offering it. Similarly, fish grown in Athens (most notably two female Panaque nigrolineatus, L190), who have never had fresh vegetables previously, became really 'addicted' to them shortly after their arrival in Manchester. These fish currently ignore the food they were brought up on in favour of the vegetables.
Finally feeding is related to natural behaviours. Natural grazers have not got the bodily capacity to keep in their digestive organs large amounts of food which they will subsequently process to extract nourishment. Their digestive system is designed to process quickly small amounts of food as they continue to consume. This in turn indicates that one feeding a day cannot by definition be sufficient for them; by the end of it, they will still be hungry.
Well fed fish, on the other hand, do not manifest “greedy” behaviour at all. Tabby, our 44cm male L25 will only consume 1 big mussel or 2 prawns at a time, no matter how much food there is in the tank. (4) Give him less and he is out searching. Give him more and it will stay uneaten at the bottom of the tank. Don’t feed him at the usual time and he will be out at the front of the tank, waiting for you. If you delay for more than half an hour he and his tankmates will be swimming up and down the tank looking very unsettled!
The same holds true for all the fish we keep. Our P. managuensis will come to the front of the tank twice daily, morning and night, wagging his tail and shaking his head - that’s his way of demanding his meal. He will then rise slowly to the surface opening his mouth ready to get his breakfast or dinner, as the case may be. The rest of the time he will ignore our presence or play with us, but there will be no food requested. In fact, if one mistakes his behaviour as requesting food and offers him a small treat, he will just let it drop at the bottom of the tank uneaten.
A more gruesome example – but one that hits the nail of greediness on the head – was given to us by one of our male P. dovii, Kerry. Kerry was the smallest of our P. dovii and was in danger of being killed by the others, so we placed him, temporarily, in a tank with blue fin panaques (L239). (5) As the fish co-existed happily, without any ugly incidents, we left him there; for over 8 months there wasn’t the smallest sign of aggression. Until, one day, we missed a meal. Next day we found one of the panaques eaten tail upwards (the head was left untouched – clearly Kerry “knew” it was a dangerous part to swallow). This was an instance of “natural” feeding for the P. dovii, i.e. he had to provide food for himself as he would in nature. He didn’t kill the fish for fun – so the possibility of sheer aggression was clearly excluded. He didn’t eat all the colony, which he clearly would do if he was “greedy”. He killed one – and ate it (interestingly, in body mass this fish equated to the usual amount of food he consumes daily). The incident was an one off – next day feeding resumed as per normal and this behaviour was never repeated for all the time Kerry shared tank with the L239s.
“Greedy” behaviour can also be observed for a variety of other reasons. Boredom is clearly one of these. In nature, fish engage mainly in four activities: they feed, they play, they fight and they mate. Deprive them of the possibility to do the three and all they have remaining is to eat – and they will do so. A sound tank, with appropriate tankmates, will allow for a more natural behaviour and exclude the possibility of comfort eating.
The fallacy of the statements we call “myths” in this article also lies in another consideration. They are “blanket” statements, pertaining to hold true for all the fish at all times. It may well be the case that some fish should be fed twice or three times daily usually or at certain times but try doing this to a predator like Pseudoplatystoma fasciatum and you are doing it no favours. This fish needs to eat good meals that will fill it up and then be left unfed for a day or two, until he digests its food. In short, feeding habits need to respect the way the fish eat in nature, their digestive system and their taste preferences.
It may well be the case that what we offer our fish is quality nourishment, but is this enough? Well, if the fish manifest a “greedy” behaviour it is clearly not. Sound feeding practices will result to fish coming to eat only when they should do – in which case food should be offered.(6)
3. The famous 2 – 3 minutes rule of thumb
Feeding habits vary between species. This may sound like stating the obvious but consider it in conjunction with the way fish are supposed to be fed. Some fish will run to the food, in which case a feeding session of 2-3 minutes will be more than sufficient. Our Paratilapia sp. "Andapa", the Parachromis managuensis, or the Paretroplus menarambo are prime examples of this. In fact, they need less than the 3 minutes. The P. sp. "Andapa", the P. managuensis or our Datniodes pulcher will fill their mouths with all the food they can put in (the Datniodes take about 40 seconds to put in their mouths 4 big mussels each) and then retreat to a corner to chew it. This is quite natural: these fish are predators. They have not got the luxury of taking all day to hunt and eat and when they do hunt they must be able to get their prey in the mouth or else somebody else will. Except if one is feeding really small morsels of food and the fish need to come out for more, feeding of these and other similar species usually takes less than a minute.
But even amongst predators there are differences due to personal preferences. Take the P. dovii for example. Two of our three dovii absolutely detest people watching them while they eat. It doesn’t matter what you offer – they will not come out to eat while you are there – or around. The only way to ensure they have eaten is to offer the food, then return an hour later to ensure it is eaten. How do you apply the 3 minutes rule here?
Add to this that both in community tanks and in species tanks, when housing primarily (but not exclusively) predators, there is a hierarchy to be respected. The top male eats first, the others follow in order. In these cases, removing the food after three minutes, or offering as much as can be eaten in three minutes will only ensure the top guy is fed. The rest will be left uncatered for.
On the other hand, natural grazers like the Etroplus canarensis, the L18s or the L47s, members of the Panaque genus etc need to eat constantly. They enjoy taking small quantities of food over a much longer period of time. Collectors confirm that wild caught specimens of catfish are kept unfed in dams for up to five days before shipping in order to excrete all they have eaten so there is minimum ammonia released in the shipping bags. This only points out at the fact that the fish, in the wild, eat constantly.
Even when full (in theory) the E. canarensis will occasionally nibble on vegetable matter, if available in their tank. The fact that such matter needs to be available in the tank is clearly manifested by the following behaviour: if there are vegetables available for them to nibble “as and when” they feel like it, the fish will be quite “composed” when staple food is offered. They will also nibble at this, but won’t be in a great hurry to do so. If, on the other hand, there is nothing available during the day, the fish will “rush” to the food every time it is offered – and will eat rather speedily. It is important to note that in the second case the fish are not manifesting a “greedy” behaviour. They will come to the top of the tank “asking” for food four times daily (as opposed to the two required when vegetable matter is available). They will consume a set amount of food (usually about 2-3 pellets each) and if more is available it will remain uneaten. The rest of the time, they will neither ask for nor accept any food if offered.
Trying to apply the 2-3 minutes rule in a tank with ex-Cichlasoma pearsei will severely disappoint you. This fish eat slowly and gracefully, no matter how hungry they are. Puntius denisonii (torpedo barbs) and Trichogaster trichopterus (gouramis) are very much the same, particularly if they are in a community tank with bigger fish around.
Carassius auratus (goldfish) are a very interesting and commonly misunderstood species when it comes to feeding. They are supposed to be voracious eaters, consume an unlimited amount of food and produce immense amounts of waste. If at all valid, the three minutes rule should apply to them.
Well, not quite. Some years ago we had an experience which we would like to share with you: At the time, we had a couple of Juwel tanks with about 60 goldfish (mixed orandas, black moors, common yellow goldfish etc). The tanks were getting algae and to counter this we were advised to introduce catfish (Ancistrus sp. and P. gibbiceps). We did this and we soon noted the following: the goldfish worked out that their food (which was mainly floating pellets), if not eaten immediately, was getting sucked by the internal filter and remained at the slots. So they did the obvious, which was to eat the sinking tablets offered to the catfish first and then go to the filter and eat their pellets too. This way they consumed an enormous amount of food, while the cats were left hungry and very frustrated.
We tried different things to stop this from happening, none of which bore any significant results. The goldfish always found a way to snatch the cats’ food before eating theirs – and no amount of food seemed to be enough for them. Until, that is, one of these tanks got planted.
The goldfish ate the plants in about three days – but during this period they left the food for the catfish uneaten. Seeing this “preference” we continued offering plants and vegetables to goldfish and the same behaviour continued. The goldfish would demolish the fresh green food and that seemed to satisfy their appetites. So we planted the second tank too. Soon after, both tanks were heavily planted with fast growing plants while additional vegetables were on the daily menu (spinach, kelp, lettuce etc). In a couple of months it was obvious that the goldfish were quite content grazing on the plants and vegetables all day – to the point that they started eating less of their staple food and nothing at all of the catfish food. It was clear that the previous feeding regime of once or twice a day for 2-3 minutes was forcing the fish to manifest an insatiable appetite.
We have used the same “trick” when we noticed that our young brood of Paratheraps fenestratus were excluding the L128s and the L200s from feeding, by attacking the food before the cats could get to it. This came to an immediate stop the minute Ceratophylum demersum and spinach were placed in the tank. The P. fenestratus were quite happy grazing on it all day, thus leaving the cats’ food for the catfish.
With these considerations in mind we would suggest that the 2-3 minutes rule is an erroneous way to approach feeding, a fossil of the past (when limited amount of species were kept in aquaria and the methods of filtration were not as advanced as they are today) which needs serious reconsideration. It is supposed to indicate the amount of food one should feed rather than the time in which this food should be consumed. It fails to do so firstly because it is not applicable to a vast number of species which are now available in the hobby and secondly because amounts should be indicated in grams per size of fish rather than consumption time.
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