Originally Posted by Fishyfins

i hear what your saying, and i believe alot of it simply comes down to experience, or just pure science.

what you say about trace elements is correct. when i said dangerous, i do mean such things as iodine. ive known far too many fishkeepers who have overdosed on such trace elements (on the advice of shops and the internet), and lost their whole tanks as a result. to me personally, who only keeps a selecton of soft corals and small motile inverts, i generally dont bother with anything but calcium, and the trace elements in the salt mix i use. if your keeping SPS corals, then it does need to be done properly, with adding the chemicals, and im sure many reefkeepers would employ more costly methods when doing this... it just makes sense to do so.

as for live rock. again, what you say is 100% true, it would be cheaper to buy second hand. though of course, with any such transaction, you run the risk of fraudulent traders, and end up with rocks covered in aptasia, hair algae, or even worse. of course, the risk does exist if you buy new as well i suppose, though id say its a lot less prevolent. the amount of times ive seen aptasia covered rock on ebay XD

now, the next point you make, about stability, is an interesting thing. ive worked with marine tanks from as low 20L, to about 1000L. as you say, the general rule is that the larger a tank, the more stable it is. however, i have had many examples of exactly the reverse. here is an example: my father keeps a 200L marine tank in his living room. this tank has been up and running for about 5 years now (in this current form anyway). now, he has a good sized external filter, and uses all the correct equipment, an does things generally well. however, he uses very little live rock, and has very few inverts in there. the tank is also lightly stocked. the water chemistry is forever swinging, fish are lost frequently, and the waer is generally not very stable.
in comparison, i keep a small 90L marine tank in my bedroom. heavily stocked, all the same brand and style equipment (just smaller cos of the tank). i also keep a lot of live rock in the tank, and a lot of reefcleaners. so, the only differences are that mine is smaller in volume, and has more fish stocks, rock and inverts.
now, my dad does a water change every week, and its needed, as nitrates and phosphates rise quickly, and alae takes over (nasty hair algae). my tank (which has been running for 7 years might i add), requires a water change once a month, and even then, all levels are within acceptable levels, (i only do it out of my fishkeeping pride). ive also only lost 1 fish in those 7 years.

Chances are, assuming you and your father live in different areas, that the water you are using varies in quality at source (or, in other words, the coldwater inlet pipe). Water that is high in nutrients and silicates is harder to 'purify' using reverse osmsosis, resulting in fishkeepers having to replace membranes and filters more often and make use of de-ionization. Water pressure can also have an effect on the quality of water that leaves the RO unit.

It's also worth considering that standard biological filtration provided by power filters normally turns into a nutrient factory after a while. Biological filtration breaks ammonia down into nitrite (as you know) and then into nitrate, phosphate and nitrogen gas. However, the process ends there, with nutrients simply building up until they are removed by whatever means.

The use of live rock is a much more effective method of biological filtration in marine tanks, and it normally results in lower nutrient readings. Since a larger percentage of biological filtration in your tank is carried out by live rock than in your father's aquarium, the nutrient readings will surely be smaller. Also don't forget to apply the other factor on varying water quality which I mentioned above, this too has a significant bearing.

Let's look at an example. Let's say that we had two tanks, one fifty gallons and the other five gallons. Each one was placed in more or less the same spot in a room, away from heat sources, windows and doors. Both tanks were filled with untreated reverse osmsosis water and a 150 watt heater placed into both with two thermometers. Using a stopwatch, measure the differences in time that it takes for each tank to reach 25 degrees C exactly. The larger of the two tanks will take longer to heat up because the larger volume of water is more stable and isn't influenced so easily in temperature.

Obviously the science and experience are contradicting eachother, however my own experiences tell myself that larger aquatic environments are more stable.

now, obviously i have experience, and to me, my father does nothing wrong. ive tried to fix his problems, as have other experts, but his tank just wont stabilise. yet mine is a wonderfully stable environment with few problems. and this isnt the only example ive seen of this, ive had many cases where this exact situation has played out, with smaller tanks generally being more stable than larger tanks. i mean, im a graduate of geography, i know the science behind it, and what should happen. the only concuion i can draw is that the higher percentage of rock and inverts in my tank leads to the smaller tank being far more stable. so yes, the science is behind you on this one, but i have alot of personal exerience to go against it. in general, fte studying many examples, i can safely say ive found more smaller tanks to be stable than large tanks (in marine environments anyway, and all the stable tanks have had huge amounts of rock and inverts.... coincidence? i think not).

Originally Posted by Fishyfins

and all the stable tanks have had huge amounts of rock and inverts.... coincidence? i think not).

Originally Posted by Fishyfins

each to their own indeed. not wanting to argue, but i enjoy a good debate on the science of marine keeping