Skip to content Where Reefkeeping Begins on the Internet

Personal tools
You are here: Home » Library » Aquarium.Net Article Index » 1296 » Splash and Monitor Aquarium.Net Dec 96

Splash and Monitor Aquarium.Net Dec 96

Sam Gamble discuss the dynamics of a sand bed sytem. December 1996 Index for Aquarium Net, Aquarium Net has numerous articles written by the leading authors for the advanced aquarist

Splash & Monitor

by Sam Gamble

Now that the parts are in place, the switch has been thrown, we have to observe and maintain the results of our labor. We need to look for leaks and see how the ecology is doing.

In the last section we built our beginning system with the idea to start with a lowered organic content, but a potentially high microbial content. The word potentially is used because of a couple of important things about the population dynamics of bacteria (microbes). Microbes need food (energy and building blocks), and an environment in which to expand their populations (colonies). The rate will be effected by each. The sand is used for both; collecting food and a place to live. There is a spectrum of species interacting in this environment putting in place all mechanisms of metabolism, competition, and succession. There are no absolute guarantees of how the microbes will react. We set the stage and the laws of nature play it out. Until they do, the environment we construct is a potential event. If we have done it correctly, potential becomes a reality.

Hopefully, starting with the deliberate construction of a "low load" environment will give the desirable microbes a competitive edge for succession into the empty niche (non-living sand). Food converted to energy for growth, is the essential factor for building blocks in new colonies. As this biological event happens, we can monitor and adjust things a little to lend a helping hand if necessary. This is a very dynamic period for macro environments and the micro environment within. A resulting important characteristic will be fluctuation or a state of "flux".

With that in mind, we need to check a few things to see how ecology of the microbes is progressing. First we need a standard for comparison. Whether is's the ocean's reef site or the latest trend of parameters published in books, magazines, or newsletters, we need a baseline. There's some variance and debate regarding "standard parameters", so I will try to be midline.

While your new tank is "fluxing" it's muscles, don't expect to see textbook figures. If you do, that's great, and stick with the consistency of what you are doing. If you don't, make changes slowly and deliberate. Crisis procedures are not necessary. A good example of parameters is:

pH 8.0 - 8.2
ORP 200 - 300 mV
NH3 may be a trace
NO2 may be a trace
NO3 starts at near zero, then builds to 10 - 20 mg/l
DO 5 - 6.5 mg/l (fluctuating with microbial blooms and bioload)
Temperature 76 - 78 degrees F.

at this point the topic of trace elements is not crucial.

Right now in the microscopic world that controls nutrient cycling, there is a gazillion things going on. We just hope they can work it out, the way we want. Fortunately there is a natural tendency to do so if enough of the integral parts are present. The concept: If you are trying to maintain an aquarium you must consider the main culture you wish to preserve and then understand that countless microscopic events must happen to maintain the macro cultures. The best way to understand the system is to understand the single cell and what it needs to promote its' equilibrium (Jones, 1996).

In a new environment instant equilibria simply won't happen. Equilibria is a difficult goal to achieve even in a cured closed system. The sand bed system's goal is to properly maintain as many compounds and elements as possible at natural and desirable levels. The idea brings our attention back to the cell and its activities within specialized environments. Our ability to use microbial populations of cells stems from what we measure as ecological variables, i.e. physical and chemical factors and the properties of the microbial populations themselves, such as their distribution, densities, metabolic requirements, and activities.

One ecological variable that is important, but seldom measured is oxygen. In regards to a curing system the amount of oxygen used as opposed to oxygen being supplied is very important. Blooming microbial populations have localized biological oxygen demands created by respiration in their metabolisms at surprising rates. It's not uncommon to see mysterious deaths, when things like ammonia are measured to be within specification. A clue is the fact that the mortalities happen at night when oxygen levels are naturally lowest and carbon dioxide levels the greatest. Another clue is the fact that most mortalities are associated with the bottom. This may include a benthic organism or a fish that is resting during the night near the bottom.

Increasing aeration will help. Addition of venturi power heads will also help more to safeguard low oxygen levels caused by respiring aerobic and anoxic microbial populations. They are growing just as fast as they can, using oxygen in the process. Their life is simple; transform energy, expel by-products, and produce new growth. Food and reproduction, life couldn't be easier. All the heavy breathing uses oxygen though.

Without the aid of an expensive DO (dissolved oxygen) meter, the measurement of pH can be a relative index. Keep in mind pH measures hydrogen ions and not oxygen. Caution must be used interpreting pH as the only sign of low DO. It's a possible clue, not complete evidence. However, when pH declines it is usually an indication of microbial activity, thereby a use of oxygen. The mechanism how this happens is complex, and due to natural buffering capacities, it is also short lived. One of the attributes of a sand bed system, is to buffer itself and stay out of the red zone; low pH.

As always when you sample for pH it is important to be consistent in sampling time. It is best to sample in the morning, as close to the time when the lights come on, as possible. There is a very important diurnal cycle between oxygen and carbon dioxide that fluctuates the amount you measure. This is an important consideration anytime you measure pH . Test it yourself by taking measurements every four hours for a twenty four hour period. It will surprise you. It's also a good indication of the varied microbial populations and how their metabolisms differ. Quoting a pH figure as if it were written in stone, without consideration of the fluctuating cycle, is confusing to its purpose.

The pH of an aquarium affects microorganisms and microbial enzymes directly and also influences the dissociation of many molecules that indirectly influence microorganisms. The pH determines in part the solubility of CO2 influencing the roles of photosynthesis; the availability of required nutrients, such as ammonium and phosphate, which limit microbial growth rates in many ecosystems. It's easy to see then that allowing an observed decline continue can be harmful to the whole ecology. Alkalinity maintenance, buffering, or water changes may be needed if an extended decline below the parameter is observed. But, increasing pH DOES NOT increase dissolved oxygen!

The ability of an organism to carry out oxidation-reduction reactions depends on the oxidation-reduction state of the environment. In solution, the proportion of oxidized to reduced components constitutes the oxidation-reduction potential or redox potential. We also call it ORP. It has become very popular to measure ORP of aquariums to get a grip of the general reactability or organic load in the water. Usually, the ORP mV reading is lower for a new tank and increases as it cures. The figures listed are for a newly established system.

The ORP is greatly influenced by the presence or absence of molecular oxygen. For example, heterotrophic activity keeps the ORP of aerobic natural waters at 400-500 mV, lower than expected for water fully equilibrated with the atmosphere. In cured aquariums the numbers range even lower at 300-400 mV. Low redox potentials may be caused by extensive growth of heterotrophic microorganisms that scavage all available oxygen. Such is often the case in developing or polluted ecosystems where microorganisms utilize the available oxygen. Here again, is another relative measure for biological oxygen demand; low ORP.

As the new aquarium starts to settle down a little, we often start the algae watch. The official curse of the reef aquarium. Some aquarists admit, the sole reason for the time and trouble of building a sand bed system, is to get away from slime and hair algae maintenance. Well, your odds are better, but you may still see some of it. You have constructed an environment that is less conducive for the curse. Biofilms and algal mats are a natural part of benthic ecology. It may start with early colonizers like diatom biofilms (usually brown) and proceed to cyanobacteria (red slime) and end with the green hair algae in a luxurious, well formed mat.

It's natural and will sneak into just about any aquarium. It could also even play an important part in break in procedures. The succession needs only three things; nutrients, substrate, and sufficient light. Factors almost impossible to eliminate. If we have started with a low load environment this will have been shunted, not eliminated. If we have provided the benthic microbial populations with the building blocks to quickly produce their ecological profile, the possibility is greatly reduced. Nutrients will be more effectively used and cycled for purposes other than a biofilms and algal mat development. The how and why was the subject of a three part series "The Algae Curse" in FAMA in 1995.

In general terms, the abundant appearance of nuisance algae and diatoms is an indication of the lack of equilibria, or developing equilibrium. This fundamentally involves using energy that is the transitional result of nutrients (food for cells). If we have been successful in building and maintaining our new aquarium, micrbial equilibrium should eventually result. There is the need to fundamentally picture filtration in a new light, since the introduction of a living sand "filter" has been employed. In days of yore, filtration implied removal of nutrients. Sand bed systems are based more on ecology and energy cycling. Energy is shared not removed. Nitrification is an ally, not the enemy. Phosphorous is a source of energy and a building block for reproduction and growth, not the devil himself in disguise as algae.

In the next segment, I will start illustrating some of the problems that have occurred to some sand bed aquariums and get into the details involved with cause and remedy; Rx and Tx.

Question & comments,

Sam Gamble 102170,3150 CompuServe

Created by liquid
Last modified 2006-11-23 01:37