In the present state of the hobby, maintaining a successful reef aquarium can be rather easy. With a reasonable, if not comparatively modest, investment of time and money, anyone can enjoy a healthy display of hardy and beautiful reef creatures. Yet after enough time spent in the hobby with a successful tank, you might still see other extraordinary tanks that make you wonder, “What are they doing different?” And you might hear stories of challenging species living many years beyond the norm in systems that seem to be the same as your in hardware and husbandry. But is the difference simply luck or good fortune? Almost certainly not - especially in the case of species longevity, which requires deliberate effort and consistent husbandry that stands the test of time. To sum it up in a word, the difference is finesse. Uniquely successful aquarists tend to have an arsenal of good habits that is thoughtful, tidy, and appears to be not very different than the norm, yet cumulatively sets them apart distinctly from the masses. 

In this article series, I intend to cover some key tips and tricks to better reef-keeping techniques that will quickly and noticeably improve the success of your aquarium. I often like to refer to such tidbits as “things you though you knew.” Many suggested improvements will not surprise you, and most I expect will make good sense and perhaps be familiar. But it’s easy to otherwise forget such good habits and get into a routine that becomes a bad rut. Indeed, we all tend to lead busy lives. However, skipping a monthly water change, for example (that might only take 30 minutes or so), seems to be quite remiss when companion dogs and cats require far more daily maintenance and attention. Do keep it all in perspective and be diligent about putting in extra effort for good aquarium husbandry, particularly when it requires so very little time. It will pay dividends in happiness for you and better health for your aquarium.

The first and single-most stimulating thing you can do for aquarium vigor is to improve water quality; do more frequent water changes. It is completely lost on me why so many aquarists resist doing regular and hearty water exchanges. The benefits are quickly apparent, the cost of doing it is rather inexpensive, and the cost of not doing it is equally motivating (poor livestock health or premature death). In the US, the old rule of thumb is to exchange approximately 20 - 25% of the system water per month. Yet this guideline was established decades ago with aquariums that were necessarily understocked for the limitations of technology at the time, and an inability to keep many animals per tank. A four feet, or one meter, long aquarium in the 1970’s or 1980’s could only house, for example, a Zebrasoma tang, pair of clownfish, some damsels and perhaps a small wrasse… presuming the undergravel or box filters were maintained well! To think of the coarse media used for bio-filtration (sintered glass, crushed dolomite, non-carbonate gravel, etc.) is no wonder why tanks had to be stocked lightly. As such, modest water change schedules were tolerable for the typically lighter bio-loads. 

In today’s aquariums, however, the amount of biomass banked in live rock and live substrates (sponge, algae, worms, bivalves), plus the increased availability and use of fishes is far greater than decades past by a scale of magnitude. Thus, antiquated rules of thumb on water change schedules are dubious if even useful. Regardless of what decade one keeps fishes in, however, heavy bio-loads simply require more aggressive processing of organics. While we still cannot quantitatively assay all undesirable elements of aged aquarium water (and remove them) while measuring and supplementing all known (missing) desirable elements (or the rate at which they are removed), we can still keep an even keel on water quality by dilution. It’s an old adage, but, “The Solution to Pollution is Dilution.” Live by these words and you will enjoy greater success in the hobby! Regular and frequent water exchanges dilute known and unknown “nasties” while replenishing known and unknown desirable elements to aquarium water.

The size of water change needed per tank varies not only on bio-load, but on several prominent aspects of husbandry, all focusing on nutrient export. More aggressive protein skimming, carbon and chemical filter media use, and vegetable or animal filtration (filter feeders and macroalgae refugiums, e.g..) can alleviate some of the burden on water quality and reduce some of the need for larger water changes. But we cannot avoid water exchanges altogether. Do consider that even with a 50% monthly water change, 50% of the undesirables, and depleted desirables, are still left behind. And those unfavorable “halves” accumulate and amplify month after month. This is the impetus, in fact, for aquarists with smaller marine aquaria to do 50%+ water changes weekly. They are largely spared the need for protein skimmers, dependence on heavy chemical filter media use/exchanges, and the alchemy of estimating how much of which magic elixirs (supplements) must be added. Best of all, it is all done at a very modest expense of mere tens of dollars per year in extra synthetic sea salt.

Although it may sound remarkable at first to do such large water changes, it is not unnatural by any stretch of the imagination. Is there any better example of the power of dilution than the ocean itself? If you spend any time at all on living reef, you will be astounded to see how much water is exchanged in a moment: millions of gallons of water in flux within sight. Add to that the fact that so many popular reef creatures are intertidal, and we have a good argument to start with for the tolerance of reef creatures to hearty water changes.

There comes a point, admittedly, where large water changes are not cost-effective in light of the alternatives (supplementation and aggressive skimming, ozone, carbon use, etc.). Larger aquaria themselves by nature are more dilute for their volume (generally less weight of fish per gallon of water) than smaller tanks where overfeeding and overstocking will concentrate in and cripple water quality faster. So instead of doing 50% or larger exchanges, you might only need 10 – 20% weekly water exchanges. This is, in fact, what I recommend most folks start with, and ramp up if needed. The point of the matter all is that smaller and more frequent water changes are better than doing the task monthly or less often.

Under the best of circumstances, water quality in the aquarium after one month typically strays unfavorably downward in pH. It certainly increases in dissolved organics. Water clarity from discoloration becomes darker, however inconspicuous that might be to the naked eye during casual daily inspection. In heavily stocked reef displays – allelopathic compounds (chemical warfare) between corals, plants and algae amplify. Phosphorous and nitrogenous compounds inevitably accumulate too. The list of challenges to water quality goes on. Now instead of allowing these dynamics to crescendo before reducing them abruptly with a large monthly (or less often) water change, the smaller, more frequent water changes will dull the peaks and valleys of such swings in water quality to minimize the stress on the tanks inhabitants.

You don’t even have to do larger total (volume) amounts of water exchange on tanks with a light bioload. Instead of doing, say, 20% per month on a lightly stocked large display… you might do 5% per week. Monitor aspects of water quality in the interim to insure that the modest exchanges are enough though (look to see that nitrates are not increasing for starters). Informal experiments have been done to compare if larger monthly water exchanges were better for water quality on testable parameters like nitrate than smaller weekly exchanges. In such trials where the same total volume was exchanged either way, the larger monthly water changes actually had a slight edge on the smaller weekly events. What the statistics do not reflect, however, is the stress of exposing livestock to greater extremes of water quality for longer periods of time by monthly water changes. Greater studies on allelopathic competition in time will undoubtedly, in my opinion, underscore the need for better attention to water quality in marine aquaria. It reminds me of the mantra that good and bad things alike should happen slowly in aquaria; small, frequent water changes support this wisdom.

Water quality issues not only affect livestock directly, but play a role in hardware applications as well. It’s no secret that lighting issues are some of the most actively discussed and hotly contested topics in the aquarium hobby. How ironic is it then to see aquarists spend many hundreds of dollars on lighting hardware and operation (replacement lamps, electricity, etc.), only to ignore the fact that poor water clarity (color) is severely handicapping the delivery of quality light to photosynthetic reef corals and invertebrates?!? Please don’t just take my word for it though; take the time to notice the difference in color between new synthetic seawater versus aged water from the tank when compared side by side in clean white plastic buckets. To make matters worse, the difference need not be great to have a significant effect (reduction) of light in the water. A tinge of color can reduce the penetration of light at depth dramatically. For clarifying issues like this, the use of a lux or PAR meter for measurements of light is, well…. illuminating (pardon the pun)! If you cannot afford such instruments, look to the local aquarium club; many reef clubs will hold a small fundraiser where each member contributes a few dollars for the group to purchase and share a light meter (decent models can be bought for $150-300, typically… Apogee brand has been popular with aquarists). The benefits of using a PAR meter are many.

photo caption: "Even with monthly partial water exchanges, aquarium water can become noticeably discolored. Even a slight discoloration significantly reduces the penetration of light at depth! Photo by Anthony Calfo"

Beyond the measure of useful light (to photosynthetic creatures), a light meter can give a revealing indication as to when lamps have exceeded their useful lifespan. With a baseline measurement of new bulbs, you can track the degradation of light quality over time. It really is surprising to see how so many lamps lose considerable PAR value after as little as 10 months (hence the oft-cited “yearly” lamp replacement recommendations).

Another great use for such meters is to take readings in the tank for corals that are being sold or traded. Similarly, known readings from coral suppliers will help you find optimal places in your tank for new specimens. The stress of acclimation to such new light is reduced by such efforts. You can also get a concise appreciation for how significant even a small amount of dust, salt creep or debris on lamps, lenses or canopies can be. With regards for how expensive electricity is too, it’s a money saving lesson that also improves the amount and quality of light that reaches precious reef creatures. While the purchase of a light meter is a not-insignificant expense, the savings on operational expense and lighting hardware alone may recoup the cost in the short term. And for the value of typical reef systems overall… it is a small investment that provides invaluable benefits to the care of photosynthetic livestock.

In closing, some words should be said about doing a “proper” water change. Mixing up synthetic seawater is very easy and safe for doing large water changes if you follow some simple guidelines. As with all incoming water, whether for evaporation top-off or salted for exchanges, be sure to aerate and slowly warm new water for at least one day in advance. Using untreated tap water can be bad for several reasons. First of all, the dissolved oxygen coming out of mains is low in dissolved oxygen, which can be quite a shock for aquarium livestock. All tap water needs to be aerated to reach equilibrium or saturation with the atmosphere of the room that the aquarium is kept in. It also needs to

be heated slowly over hours or a couple of days to match the system’s temperature. It can be dangerous to heat water quickly and use it right afterwards in the aquarium! When pouring oxygen-poor hot water into oxygen-rich cool water, there is the risk of driving oxygen off/out of solution and even causing oxygen/air embolisms in fishes much like divers that get “the bends” from nitrogen. It should also go without saying that the salinity of new water should be adjusted to match the salinity of aged/out-going water. While plastic hydrometers are handy and durable, please keep an extra hydrometer made of glass or a refractometer on hand to check the accuracy of plastic handheld hydrometers periodically. And finally, you should not underestimate the caustic nature of newly mixed seawater. Chemical reactions in dissolving synthetic sea salt mixes take time to complete. To temper the harshness of newly mixed seawater as well as insure thorough dissolution, mix freshly salted water for some hours up to one day in advance of use in the aquarium. Follow these suggestions and you will be on your way to finessing your own successful marine aquarium!

with kind regards, Anthony Calfo - March 2005