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Disease is the bane of the fish hobbyist and fish farmer alike. Why do fish get sick ? This article provides a basic overview of the cause of disease. Can we do anything about it ? The short answer is yes, and its easy - with simple preventative health management.

The relationship between stress and disease

Disease usually isn't just 'caused by bugs'. That is the single greatest misconception in health management. Disease is caused by an often complicated interaction between three main factors: The state of the fish, the environment and pathogens (aka 'bugs'). When one of these is unfavourable the fish has to adapt its physiology or behaviour to compensate. These adaptive responses, collectively called stress, intefere with the normal physiological functioning of the fish.

Chronic stress lowers the resistance of fishes to infectious agents. How ? Well, one way is that stress causes fish to produce higher levels of corticosteroid hormones. This suppresses the immune system of the fish and reduces the number of white blood cells produced. The relationship between stress and disease highlights the link between disease and poor tank management.

Overview

Glowlight tetras are small, peaceful and hardy fishes ideal for a tropical community aquarium. They originate from Guyana in South America and typically inhabit soft, slightly acidic waters in their natural habitat. However, they are fairly tolerant and do not require any special conditions in terms of water quality. Glowlight tetras are egg-scatterers and prefer to lay amongst fine-leaved plants in the early morning. Known spawning triggers include water changes and the presence of favoured spawning substrates (fine leaved plants or similar materials). The larvae require infusoria for around ten days and can take artemia thereafter. They are very easy to breed.

Overview

Dwarf halfbeaks (also known as Malayan or wrestling halfbeaks) grow to around 7cm. They are native to fresh and brackish water areas in south-east Asia. They are very common in Metropolitan Bangkok where you will find them swimming in most of the canals and ponds. Like most halfbeaks they swim and feed on the surface. They have no special feeding requirements and will eat flake food.

Dwarf halfbeaks are very aggressive but only towards other halfbeaks - they will continually snap at one another although they rarely seem to inflict any damage. They will peacefully coexist with other small fishes (so long as they aren't small enough to swallow). They are bold and tolerant of handling. They will resume eating seconds after being transferred to a new tank.

Today I had the chance to meet Dr Gong Zhiyuan, a Singapore-based scientist who developed fluorescent zebrafish Danio rerio by implanting genes from jellyfish that produce fluorescent proteins. They dont glow in the dark, but they do fluoresce (emit light) when exposed to both normal lighting and particularly under black lighting (UV).

The fish are currently available in most of your standard highlighter colours (coincidence ??) green, yellow, red and orange but there are a number of other coloured proteins that could probably be used. The fish are about to be released on the market in the US.

I asked Gong where he got the inspiration to do such a thing - why did he do it ? He said that the Singapore ornamental fish trade was the largest in the world, and he had felt - well - that such a thing would be very popular.

In the previous article I mentioned the issue of fragmentation: Its a real problem for mobile developers. Sun has long peddled Java as "Write Once Run Anywhere", but has to a large extent been bullshit - due to platform fragmentation.

To address the fragmentation issue the Java Community has been moving towards the adoption of a number of standards or "JSR"s. These mandate a certain 'minimum' set of functionality that you as a developer can expect to find on a particular device. For mobile phones, the most important standard is the "Mobile Information Device Profile" - better known as MIDP. Almost all Java-enabled mobile phones support MIDP.

There are currently two versions of MIDP: 1.0 and 2.0. At the time of writing, most of the phones on the market are MIDP 1.0 devices. However, MIDP 2.0 is beginning to appear on high-end devices - mostly smartphones such as the Nokia 6600. Its likely that MIDP 2.0 will start to become more the norm in 2005 (at least, Russell Beattie thinks so and I believe him :) MIDP 2.0 is backwards-compatible with MIDP 1.0, so if you write a MIDP 1.0-compliant app then it should work on most of the phones available today. Emphasis on should.




There are also standards for a number of optional packages.

A number of standards have been developed in order to address the fragmentation issue. For mobile phones, this means the Mobile Information Profile - MIDP for short.

Luckily there are a few standard available:

A configuration specifies a certain Java Virtual Machine and a set of core APIs. There are two (refer to diagram) - the Connected Device Configuration (CDC) and the Connected Limited Device Configuration (CLDC).

Ground Zero: Resources to get you started
Ok, enough theory already ! If you have no programming background at all, here are some resources to get you started.

Java 2 Standard Edition
You need to learn a bit of J2SE first to familiarise yourself with the general principles of the Java language - this is the most difficult and painful step. The books on J2ME assume you already know J2SE so there's really no avoiding it. Just think you'll be able to program your desk top as well !

If you're feeling stingy, there is a free Java Tutorial on Sun's Java website. There's plenty of other documentation there if you're willing to dig through the site, but its a bit of a mess. You will also need to download the J2SE Software Development Kit, which is free.

Otherwise you'd better buy a book. My personal favourite is Head First Java. This has been written in an irreverent and (occasionally) amusing manner specifically to help you keep your attention and remember things - and it seems to work. Sam's Teach Yourself Java in 21 Days is ok if you prefer the traditional textbook approach - but its a bit dull, know what I mean ? You'll have to grind through it.

Java 2 Micro Edition
If you survive J2SE you'll find this easy. J2ME is far less complicated than J2SE because the devices are so much more limited ! There is documentation on the J2ME website but for this one you really are better off buying a book. There aren't many to choose from (I'm only aware of two recent ones, and I've only read one). I've got Wireless Java: Developing With J2ME, Second Edition by Jonathan Knudsden. Its pretty good, in my opinion. It is written very clearly and concisely and will drag you straight into writing applications.

J2ME Wireless Toolkit
This contains emulators for different types of mobile phone, tools for packaging and compiling your code etc. Its simple, effective and free.

That should keep you busy for a few months If you're serious, one other useful resource is the Mobility Developer email newsletter Sun sends out every week or so (yes they do some good things). You need to subscribe to receive it, and open an account on Sun's website (free). It contains tips on how to attack certain problems and small challenges for you to work on to develop your knowledge.