Aquatic Invertebrates. (suitable in planted tanks)
Shrimp are decapods or 10 limbed crustaceans along with crayfish, cherax crabs and others.
Historically only crayfish were kept, in the last 10-15 years shrimp and other crustaceans have become increasingly popular in home aquaria.
This article will try to give an overview on owning, keeping healthy and breeding of the dwarf freshwater shrimp, fan handed shrimp and long armed shrimp as well as the dwarf crayfish(*). Although not precise the term shrimp will be primarily used to cover all of these. Because of the wide number of decapods being covered generalisations will occur and more specific details should be sought once a choice of inhabitant has been chosen.
The differing types of decapods covered include:
- The algae eaters mainly from the neocardina and cardinia species these are collectively referred to as the dwarf shrimp.
- Long-armed or macrobrachium which are opportunistic hunters and so have different requirements as far as tank mates and raising of young.
- The fan shrimp or atya, atyoides and atyoida species which can be quite large and are generally peaceful should generally be housed in groups. They are named after the specialised adaptations to their first appendages which have developed to sieve the water and fan particles toward their mouths. They need good circulation and suspended bacteria/micro-organisms to feed on often near a filter return or perched on some ornament.
- Dwarf crayfish (need to check legality of English keeping) which are as they say a smaller peaceful version of their larger cousins. Most of this group come from the cambarellus group.
Tank set-up.
A species only tank is best, unfortunately many new keepers wish to have them as part of a community (often because we have only one tank and want as much variety and interest as possible). The shrimp suffer and often hide from the fish in this type of situation depriving us of the most enjoyment and, the shrimp of the most suitable habitat. With the long armed shrimp being predators and often consuming protein, other fish, shrimps and even snails will be taken at times dependant on the particular species, again a species only tank is therefore best for separate reasons with these. The dwarf crayfish although generally peaceful, can even be harmful to each other with males to male aggression being more likely and again is most suited to a species only tank.
There will always be reports of successfully keeping varied combinations of shrimp, crayfish fish etc and it is not for me to say that these combinations will not work in individual situations, just bear in mind the basic guidelines and decide what is more important to you, hopefully your inhabitants health and welfare.
Water requirements.
For the majority of shrimp a neutral and medium hardness water is generally suitable, some species do have preferences for slightly acidic or moderately alkaline waters though a range of 6.5 to 7.5 pH and hardness levels around 10 Gh are adequate starting points in most cases. Once deciding on a specific species it would be advisable to research further its exact water requirements.
When changing water it is important to try and match the new water with the old water in respect to temperature and hardness or tds readings, I find this more important with shrimp than with fish. Most important in water is ensuring that chlorine, chloramines and heavy metals are removed prior to adding to the tank, either with dechlorinators and or filters.
With their increased sensitivity to heavy metals shrimp are more susceptible to leached ions from hot water systems in which water contact with copper pipes is longer.
Floor space is probably more important than actual tank volume and shrimp can be kept in very small containers successfully just remember it is easier to keep water parameters stable in larger tanks and I wouldn't advise anything smaller than 25 litres. Hiding places should be provided either with foliage, rockwork or ornaments this is particularly important in the dwarf crayfish species as they can be quite vulnerable whilst moulting and soft bodied.
Filters.
Basic air driven sponges are generally the most suitable, if you have a larger tank and want a more powerful pump then an intake sponge is going to be needed to stop shrimp being sucked into the filter, certainly they will happily climb on the intake and look safe, equally I will often find shrimp alive in the filter when cleaning a canister filter that does not have a sponge pre-filter on the intake.
When more circulation is needed because of higher plant levels, or for providing current to the fan handed shrimp, then larger powerheads or canister pumps are required again sponges are important with these.
Temperature.
Requirements around 20 Celsius is generally achievable in most homes without heating of the tank (your local geography and environment obviously have a huge bearing on this), if your water falls below 15 it maybe better to have a heater in the tank (I have had shrimp survive over winter outdoors in water butts) equally for those in warmer climates chillers or fan cooling is often required. Fluctuations in temperature of the tank, if slight, may actually be beneficial to survival and longevity of the shrimp.
Feeding.
It is generally considered that shrimp are great for cleaning up algae in planted tanks, in my experience if they are hungry they will eat anything, and mine always seem to be hungry. In nature most dwarf shrimp are detritovores; this means they scavenge biofilms on decaying vegetation for small bacteria, moulds, fungi and the algae that most of us know. In my experience they will also consume meaty fish treats including most frozen and live foods that I have used. If dwarf shrimp are wanted to clean algae from plants then withholding other food sources will maximise there potential algae consuming abilities. I often advocate having a shrimp only tank through which plants can be cycled for cleaning.
Specialised feeding requirements or methods are necessary for the fan handed shrimp with particulate matter that is light enough to stay in suspended in circulation for them to filter, again any style of food from flake to micro worm will be taken.
The long armed and dwarf crayfish have more ability to scavenge larger meatier foods and this can bring them into conflict with small or weakened fish, though most commonly they will just scavenge sick or dying fish (this too will be seen with shrimp- they are not cannibalistic) or other crayfish and young , more so when crowded.
Lids.
All shrimp will climb and can survive short periods out of water, especially if unhappy with their environment, water quality or tank mates, and so it is imperative that lids are used on tanks to stop accidental losses to desiccation on the floor. Equally attempts to leave a tank should alert the keeper to an issue within the shrimp’s environment that is less than ideal.
Aquatic plants.
Simple aquatic plants are probably best suited to these tanks (see easy planted aquarium -link?). Low maintenance and ease of growth allows the shrimp to still find algae and other biofilms on which to graze. High maintenance algae free fertilised tanks are a much more difficult area in which to successfully maintain shrimp. High plant growth will compete with biofilm and algae production and reduce natural shrimp food sources, there is some thought that fertilisers can be toxic to shrimp at higher levels notably copper. Carbon dioxide addition to planted tanks is another contentious issue as far as shrimp health. My experiences have been that I can keep shrimp alive in tanks with carbon dioxide injected and as yet I have not seen breeding activity, equally when carbon dioxide levels elevate shrimp activity seems to slow.
My preferred shrimp setups include moderate light no water column fertilisation (enriched substrates are ok) and no carbon dioxide additions.
Compatible tank mates.
Other shrimp, fish with specialised feeding mouths i.e. otocinclus cory's and ancistrus or other small plecs and some of the specialised surface feeding fish, although any larger fish will frighten shrimp whether predating or not.
Obviously depending on what you initially want and size of tank, choices may vary from many varieties of dwarf shrimp with the biggest concern being cross breeding of the various species to breeding tanks of dwarf crayfish in which only females maybe held with the male introduced for short breeding periods
Most aquarium shrimp strains are chosen for there high colouration. This is an exaggerated trait that reduces the shrimps camouflage abilities and tends to make them more interesting to most fish. I cannot stress enough the importance of keeping fish and shrimp separate, basically any fish that can fit a shrimp in its mouth will. Once fish associate the shrimp with food they will quickly hunt down all shrimp in a tank, the exceptions previously listed are not inclined to do this and exceptions exist to almost any rule.
If you intend to breed shrimp then again no fish is best as baby shrimp are so small that they will inevitably be eaten by even the most mild mannered of fish, just think baby brine shrimp are one of the most popular foods for fish breeders.
Even shrimp will consume dead and sick cohabitants, small dwarf crayfish have been recorded to predate dwarf shrimp and it goes without saying that the long armed shrimp will predate or pick off small sick and sleeping fish and shrimps.
Sexing shrimp
Dwarf shrimp often can be sexed by body shape, females have extended shell pieces called pleura on the tail region for assisting in carriage of eggs, males are slimmer and perhaps less coloured, males will often have longer antennae - more pronounced on the second smaller pair of antennae.
Though in certain species this is not so easy and the most correct biological way is to actually look for the genital opening beneath the shrimp. The female opening is located on the 6th body segment whilst the males is between the 6th and 8th (not much use in a 2-3cm shrimp I know).
In macrobrachium the size of the clawed first appendage is usually the easiest way to tell male from female with males having the larger claws, commonly there is a significant body size difference in fully grown specimens as well.
Fan handed shrimp tend to have larger first walking legs in male shrimp and the extension of the carapace or pleura ventrally to assist in egg carriage.
In the dwarf crayfish external genital differences are visible beneath the tail where the first pleopod shows specialised adaptations.
Of interest is the recording of partial hermaphroditic changes in most decapods and certainly the farmed interest in single sex (males grow faster and thought to be economically more profitable) rearing via androgenic hormone manipulation?
Varieties as far as breeding - 2 different ways.
- All shrimp produce eggs in the ovaries which can often be seen developing through the shell (See image above) on the back and just behind the head, at moulting these eggs, if mating has occurred pass down and through the genital opening (where sperm may have been deposited at mating) to be fertilised and held on the swimmerets or pleopods under the tail of the female
- Most dwarf shrimp take about 3-4 weeks for these eggs to hatch. If you see a shrimp carrying eggs under the tail, they are almost always fertilized.
- Some shrimp produce fully developed miniature versions of adult shrimp
- Others produce a planktonic life stage (zoea) which is free floating/swimming and requires an increase in salinity and smaller suspended particulate foods to develop to the juvenile stage.
Disease
- There is currently very limited detail on invertebrate disease, with the increasing popularity of shrimp in aquaria this may change. At present most research has been focussed on food producing species, which are not covered in this article, such as the larger decapods prawns, crayfish, yabbies, and lobsters. (Some detailed articles on disease in farmed shrimp can be found at the food and agriculture organisation of the United Nations web site fao.org).
- Good water quality and correct environment are obviously important in maintaining the health of your shrimp, as with fish many illnesses are attributable to failure to provide appropriate conditions.
- Certain medicinal products are known to be toxic to invertebrates, such as copper, acriflavine, organophosphates
whilst others are suitably safe i.e. formalin, malachite green, and many antibacterials
At present I have only experienced 2 disease scenarios.
- Fungusing of eggs whist being carried and sometimes secondary infection of the shrimp’s shell. This, in my experience, has been cleared when the shrimp shed without any specific treatment.
- And a general opaque or translucency developing in shrimp’s body, I am unsure whether this is just a failure of osmotic controls and a non specific pre death change that is seen in more than one particular illness, or an actual specific disease, I would be inclined to guess the former.
Crustaceans, and more so the predatory or aggressive forms, are prone to losing limbs. These can be regenerated at the next moult though will take a few moults to regain full size.
In farmed crustacean a shell disease is commonly noticed, this is primarily a secondary bacterial infection in damaged carapace areas, much akin to fin rot in fish; many different bacteria have been implicated. Improved husbandry and water quality should control this and cure is often seen after a moult.
Crayfish plaque caused by a fungus 'aphanomyces' infecting the soft non calcified body parts perhaps similar to what I have encountered in shrimp.
Porcelain disease of Australian crayfish due to a microsporean infection, thelonia, there is no known treatment for this at present other than removal of affected individuals.
A small flatworm temnocephalan, usually non pathogenic and can be cleared by saline baths.
An encysted worm larva, where the crustaceans are thought to be an intermediate host is also recorded.
Again from farmed lobster species a protozoan parasite is known to cause sudden deaths, paramoeba, it attacks the nervous system leading to paralysis and death usually within a 24 hour period - "aka" limp lobster syndrome
Aaeroccocus a gram positive bacteria can cause reddening of the ventral abdomen, mortality is higher at high temperatures, at present I can find no recorded antibacterial treatment success.
(*) In the united kingdom crayfish are banned as imports due to potential harm, competition to or displacement of native species.
References and other informative sites.
Bsava manual of ornamental fish second edition
jbl what-why-how? crustacea and shrimp in freshwater aquaria
biology of shrimp at the museum Victoria
internal and external anatomy of the penaeid shrimp FAO
http://www.planetinverts.com/home.html
http://www.opsi.gov.uk/si/si1996/Uksi_19961104_en_1.htm
Submitted by Fishgeek
