KAREN RANDALL

A well-planted, large tank inhabited by a group of healthy discus is truly an awe-inspiring sight.

I think the most important thing to do when planning a planted discus tank is to define your goals. If you are setting up a tank for a pair of discus that you hope will spawn and successfully rear young, the approach will be different from a tank where the primary goal is the enjoyment of watching adult discus in a beautiful display.

If you are serious about spawning and raising discus, then it makes sense to maximize your chances for success. This may mean that the best setup is a tank with a bare bottom. And if the tank has a bare bottom, it probably needs to be dimly lit as well or the discus will feel exposed and uncomfortable. On the other hand, if you are interested in a beautiful display tank to serve as home for a group of healthy adult fish, read on.

In my experience, discus aren’t nearly as “delicate” as people would have you believe. But they do need to be kept under proper conditions to remain healthy. By proper conditions, I mean clean water, warm temperatures and an environment with minimal stress and disease-free tankmates.

Just buying some discus and throwing them into an established community, planted or not, may not be successful. It is best to plan the tank from the beginning with the idea that it will house discus.

The best thing you can do to ensure success with a planted discus tank is to buy the largest tank your budget and space will allow. I would strongly discourage the use of tanks smaller than 55 gallons, and even then, you will have to be prepared to do more maintenance than average to keep ahead of the nutrient buildup and avoid algae problems. I found that with four discus in a 55-gallon tank, I had to do 50-percent water changes twice a week and run phosphate-removing resins in the filters to keep up with the waste they produced, even though I fed more lightly than most discus keepers do. Discus are large fish. Even sub-adults have hearty appetites for a diet that is naturally rich in phosphates.

The nicest planted discus setups I’ve seen have been 6-foot tanks with a capacity of 125 to 150 gallons. This size tank is big enough to support four to six adult discus, a variety of small schooling fish and a few bottom dwellers. With this level of stocking, the nutrient load will still be manageable assuming the tank is densely planted and growing well.

Initial Setup

Rockwork and wood (like driftwood) must be chosen with care for a discus tank. Use only well-aged driftwood and make sure any rockwork used does not have sharp edges where the discus could get hurt should they become frightened and run into it. I’ve seen a discus scrape itself badly on lava rock it was attempting to hide behind. While the scrapes healed without incident, it would have been easier to prevent the injury to start with.

Now comes the question of lighting. We’ve all heard that discus prefer dimly lit tanks. Well, the last time I checked, the sun in the Amazon basin was just about as bright as many other places in the world. Where do discus go to avoid the sun or hide if they feel threatened? Into the shade, under vegetation! Granted, in the typical discus biotope, this shade would not be in the form of aquatic plants, it would be forest canopy and tree roots. But the premise is the same. It’s not that the light level needs to be lower, it’s that the discus need to have a way to escape it if they so desire. Discus do absolutely fine in tanks with an excess of 3 watts per gallon of light as long as there is plenty of cover. Interestingly, they won’t even avoid the brighter areas of the tank as long as they feel they can hide if they want to.

Exactly how much light you will need or want will depend to a great extent on your water source. If your water is quite soft, you may be able to grow enough species of plants in moderate lighting and without supplemental CO₂ that you choose to run the tank with around 2 watts per gallon. If your water is harder, with a higher carbonate hardness (dKH), you will find that your plants grow better (and therefore handle the nutrient load better) with a light level closer to 3 watts per gallon and with the addition of supplemental CO₂.

Do not add supplemental CO₂ to a discus tank that is poorly buffered (dKH below 3). While high CO₂ levels and large pH swings are not tolerated well by many fish, discus are particularly intolerant of this treatment. Many people are under the impression that you can only keep discus in very soft, acid water. While this may improve your chances of breeding discus, it is not necessary to maintain them. Discus can live to a healthy, happy, ripe old age in water with moderate amounts of both dKH and general hardness. In fact, they will do much better in steady, reliable conditions like these than they will in the tank of an aquarist who is constantly fiddling with hardness and pH, but cannot maintain stability.

If you do decide to use supplemental CO₂, it is best to use a pressurized tank system with a reliable regulator and needle valve. Again, the goal should be stability. Reasonable amounts of supplemental CO₂ will not harm your discus. Rapid or large fluctuations in conditions will.

Filtration in the planted discus tank need be no different than any other planted tank, except that the tank itself is probably quite a bit larger. Also, because of the value and size of the fish in question, it is probably better to err in the direction of too much, rather than too little, filtration. Large canisters or a wet/dry filter are probably the best choices.

I am often asked what plants can be successfully grown at discus temperatures. If you are keeping your tank in the low to mid 80s (degrees Fahrenheit), there are very few commercially available aquarium plants that won’t do fine. The important thing to remember is that when you increase the temperature, you increase the plants’ need for light, CO₂ and other nutrients. As long as the tank is adequately illuminated and the plants are well nourished they will do fine. There are no plant species I have worked with successfully in my other planted tanks that have failed at discus temperatures. For that matter, I have had periods during heat waves where the temperature in many of my tanks have remained in the mid 90s for up to six weeks. Some species have had slower growth during these periods, but all have survived.

As with any other new planted tank installation, plant heavily from the beginning. Make sure the initial planting is heavy on fast-growing species. If possible, concentrate on those that you know do well in your water conditions. If this is your first planted tank, some suggestions are: water sprite (Ceratopteris thalictroides), water wisteria (Hygrophila difformis), Hygrophila polysperma, Rotala rotundifolia, Vallisneria sp., frog bit (Limnobium sp.) and Salvinia. Some larger swordplants, such as Echinodorus bleheriand E. ’Rubin, should be introduced in the early stages, as well. This will give these plants a chance to settle in and stretch toward the surface and will give young discus plenty of potential hiding places when they are finally added to the tank.

Stocking the Tank

While Siamese algae eaters (Chrossocheilus siamensis) are extremely useful algae eaters in many planted tanks, they do not work well in a discus tank. They will not bother the discus in any way, but they show a strong preference for discus food over algae. You will soon have submarine-size siamensis, and, while they are still enjoyable fish in their own right, they won’t do a thing to keep algae under control in the tank!

Do not under any circumstances use Chinese algae eaters (Gyrinocheilus aymonieri). These fish are aggressive and territorial under the best of circumstances and have a much stronger liking for discus slime than they do for algae. Larger “pleco” species have been accused of the same behavior, although experiences seem to vary from hobbyist to hobbyist. Do not feed your algae-eating fish or fertilize your tank for another two weeks.

At the one-month mark, you can begin filling in with your schooling fish. My personal preference is for a large school of a single species of tetra. A hundred cardinal tetras (Paracheirodon innesi) make an awe-inspiring sight swimming up and down the length of a 6-foot tank! Avoid boisterous or nippy species like serpae tetras (Hyphessobrycon callistus) or black skirts (Gymnocorymbus ternetzi). For variety, any of the pencilfish (Nannostomus sp.) make attractive, inoffensive additions to a discus community, as do hatchetfish and splash tetras of the genus Copella.

At this point, it is also appropriate to begin your regular maintenance schedule. This will include weekly water changes of at least 25 percent and the regular addition of a good trace element fertilizer. It is an unusual discus tank that ever needs supplementation of nitrogen or phosphate.

The area where people are most likely to get into trouble with planted discus tanks is putting themselves in a position where they need to medicate their fish. Many medications are very damaging to aquatic plants and sometimes it can take weeks for the damage to become apparent. The best way to avoid this problem is to make sure that all fish introduced into the aquarium are healthy. I can’t state strongly enough the importance of adequate quarantine procedures in ensuring the success of a planted discus tank. Quarantine all new purchases for a period of at least two weeks, preferably a month, before adding them to the display tank.

While I am building up the stocking levels in the main tank, I get my young discus off to a good start in a smaller quarantine tank that is separate from the tank I use to quarantine the other fish destined for the display. I would steer clear of newly imported or wild-caught discus for this type of tank. I wouldn’t even buy pet store fish. Buy a group of young discus directly from a reputable breeder whom you trust to supply you with clean, healthy stock. Even then, keep them in your quarantine tank for at least a month. Make sure they are healthy, eating vigorously and behaving normally. If you do encounter health problems, solve them now, in the quarantine tank. The effort you expend on this step will reward you for many years to come.

Your discus should be the last fish introduced to the tank — at about the six to eight week mark. By this time, the plants will have settled in and be growing well. They will be able to absorb the nutrient load of the growing discus and their feeding habits. This will help keep the water chemistry in the tank more stable. Many of the plants will have reached the surface, providing shaded areas where the newly installed discus can escape the light if they so desire. The schooling fish will have settled in as well and feel comfortable in their surroundings. Their relaxed behavior will soon convince the discus that there is nothing to fear in the environment. The fact that they will be used to your feeding schedule and waiting for you, will cue the young discus in to meal times, meaning there will be less wasted food left to feed algae instead of fish.

Feeding your Fish

Whatever foods you feed your fish, they should be fed in small quantities — if possible, a couple of times a day. It is best to get your fish into a routine of coming to the front glass at feeding time. Then you can feed them a few pieces at a time until everyone has had enough. If you feed so much that food is dropping onto the floor of the tank, you risk that the fish will not find it and it will decay, adding to the waste levels in the water.

A final word of caution. Stay away from Tubifex and/or black worms in the planted discus tank. Again, we want to avoid the introduction of pathogens into the aquarium as much as possible. While black worms are less likely to be contaminated than Tubifex, both have the potential of carrying disease organisms into the tank that will be hard to treat without damaging the plants.

Maintenance

Watch your plants carefully and let them tell you whether you need to increase trace element supplementation. If growth slows or leaves are looking as though they are losing their chlorophyll (chlorotic), it is a good sign that more trace elements may be required.

It is also a good idea to track nitrate and phosphate levels in your tank, at least for the first six months or so. Use low-range nitrate and phosphate test kits. If you find that levels are staying low, your maintenance routine and plant growth are keeping up with the nutrient input into the tank. If you find that nitrate and phosphate levels are slowly rising, you will need to increase water changes to keep ahead of the input.

At 2 watts per gallon, your tank can probably withstand nitrate levels as high as 10 milligrams per liter (mg/L) and phosphate as high as 1 mg/L without too much algae growth. If you are running the tank at 3 watts per gallon, it is best to cut both of these numbers in half.

If you find that in spite of a good regular maintenance program you are still getting unacceptable amounts of algae, the first choice, of course, is to examine your stocking and feeding levels. If you are not willing or able to cut down in these areas, you must find other ways of reducing nitrate and, more especially, phosphate in the water column.

Assuming your tap water is nitrate and phosphate free, the best solution is to step up the amount and frequency of water changes. It is also helpful to use sponge prefilters on all filter intakes to act as mechanical filters. These must be cleaned no less than every 48 hours to remove debris before it is broken down and the nutrients released. Finally, if all else fails, phosphate- and nitrate-removing resins can be used in the media chamber of your filter. These resins work quite well to sop up the last bits of nitrate and phosphate, but will not handle high levels of either substance in an efficient manner. They are also rather expensive if used on a routine basis.

A large, beautifully planted tank inhabited by saucer-size healthy discus is an awe-inspiring sight. A tank like this is not difficult to achieve or maintain. With a little forethought and ongoing attention to routine maintenance you can have a stunning slice of nature to enjoy in your living room.