----- Original Message -----

From: HL

There have been quite a lot of discussions concerning fish diseases. Well, here's my view, for what it's worth....   I have a 55 gal (UK) marginal reef tank, with a 25-gallon sump. My tank has been running for more than two years without an UV steriliser or ozone. So far, I've never had any noticeable disease or sick fish in the tank.

During this time, I've had power failures which caused the water temperature to drop as much as 10°F, pumps packing up, (once causing the system to go for 2 days without any filtration), and many other mishaps which should have affected my fish negatively. I once even dumped about 1.5 litres of skimmer effluent back into my system when I accidentally bumped the container, causing it to fall over, back into the sump!  On more than one occasion I've also (unknowingly at the time) introduced parasites into the tank by adding unfiltered "fresh" natural seawater. The day thereafter, I observed flukes (or small worms?) hanging on to the sides of my fish. After another two or three days the parasites all disappeared, again without any harm to my fish.

Now, any of these mishaps should have stressed the fish, and they should have developed Ich or some other disease, but none of the fish have ever shown any signs of illness.   I'm not bragging about this, and I'm also not claiming that it has anything to do with my good husbandry. I do, however, believe that my reef set-up, low bio-load, live rock and sand, and certain inverts, all contribute towards the health of the fish. Here are my views:

With a total stocking density of 5" of fish in the 55-gallon tank, my bio-load is very light, and so is the resultant pollution level. Because they're not crowded, the fish also live in harmony, and there are no territorial fights. This contributes to a low stress level, which helps to keep them healthy.   My Feather Duster worm, Dendronephthya (Cauliflower Coral), Leather Coral and Zoanthus polyps all eat very small (planktonic) animals. I believe they also make a meal of the free-swimming larvae of Cryptocaryon irritans (White Spot, or Ich), Amyloodinium ocellateum (Marine Velvet), and similar diseases, thereby reducing the number of parasites to a level where the fish's own immune system can protect it.  The large number of life forms in the live sand probably also prey on the adult stages of these diseases, after they fall off the fish and settle to the bottom. The Cleaner Shrimp removes the adult parasites from the fish, and the above mentioned "filter feeders" eat the offspring.

I don't feed the fish a very varied diet - mainly Tetra Bits micro pellets and Tetra Delica Ocean Plankton (freeze dried Krill), with an occasional treat of fresh fish or prawn meat. However, there is an abundance of Copepods and Amphipods in the sand and rock, and the fish regularly catch their own meals. They also get an occasional treat when the baby Cleaner Shrimps hatch (and even some of the baby Clarkii Clowns, these days), and they have an abundance of macro algae, as well as a few "bushes" of green and red "hair algae" on the rear glass, on which to browse. So, they get balanced meals, and the extended food chain helps with filtration, and with keeping the system stable.

The last contributing factor, I believe, is the fact that the fish tank water is kept at a relatively high salinity and temperature, as found on their native reefs (1.024 at 80°F-82°F). The water quality is also quite good, with ammonia, nitrite and nitrate being undetectable with my Red Sea test kits.

From: WS

I also have been musing over disease for the last few days. My tank has not been set up for anywhere near as long as yours but I too so far have not had any disease. My tank is 55 UK gal as you know and I have approx. 17" of fish so quite a high bio load. I also have a tendency to feed rather heavily.

But like you, I have plenty of living rock and sand. I have, fan worms, shrimps, polyps etc which are all filter feeders. My only additional filtration is a Backpack skimmer and I do not have a sump. I have also allowed the back two corners of my tank to become green with algae, which is where a healthy colony of copepods and amphipods tend to hang out. I actually think (just putting on my hard hat) that you can have the tank too clean in the sense that it is a sterile environment, which is why I will not have a UV steriliser and am not obsessive about a bit of algae here and there. I believe that there are just as many good bacteria as bad ones and that it is possible to find an equilibrium. You have only to look at these new human super bugs, which are resistant to antibiotics. It is my view that this is the result of indiscriminate use of antibiotics and not allowing the immune system to fight on it's own. For many years I worked with the mentally ill. I have seen people who have lived in absolute squalor, who have eaten filthy and decaying food which would have killed you or I and they were physically fit and never seemed to be ill. It must give pause for thought.

I think that you are right that the answer is to try to create an integrated environment where the livestock supports each other. In my humble opinion, if diseases keep recurring there is an imbalance somewhere and rather than treating the symptoms one should look for the cause. I think that there is a tendency to buy stock just because it appeals without considering the whole picture. I do this myself which is why I have ended up with three tanks because I know that they cannot all live together.