Zero Water Change Planted Discus Tank Proposal???
From reading through these forums I don't doubt that the premise of my proposed discus tank may leave you concerned, especially as it's heresy for anyone that has committed much of their lives to the orthodox discus keeping practices. In any case, I'm at the start of planning and researching a tank set-up which I'm afraid intentionally breaks practically every one of the normally accepted rules of discus keeping. And what I'd like to know is if anyone else has done something similar this and under what parameters?
What I'm looking to achieve is a spectacularly beautiful densely planted display tank with many beautiful healthy discus combined with a few other select species, (yeah, sure like seeing the Holy Grail, right?). And I'm looking to achieve this via an inexpensive high-tech low -maintenance over-filtered automated set-up with a fair stocking load yet ZERO water changes apart from topping off the tank occasionally with RO water and NO gravel vacuuming, as I have neither the time nor inclination to do regular water changes. I appreciate this is a contentious proposal to this group, but am hoping this can be considered with an open mind and doesn't rile everybody up unnecessarily.
I'm thinking a 78"Lx24"Dx30"W 185 gallon tank, though possibly even the 108" long 280 gallon tank instead which is hardly more costly for the tank itself. Filtration would be one (or two, as need sees fit) generic Sun Sun canister filters, which filter 530 gph and have a filter volume of 4.4 gallons. I'd have two small corner sumps at either end, one as a screened overflow intake with the other returning water along its height through vertical slots and containing the heater, and possibly a return bar with holes drilled across its length running along the bottom back edge as well to ensure some, though low current throughout the tank and the plant beds and water surface. I'd have a DIY pressurized CO2 system connected to the light timer which is run by a digital Ph controller. Lighting would be via a highly energy efficient DIY LED hood with high powered warm-white (which I think provides the most natural looking light) waterproof LED strips, as many as are needed, which are currently sold quite inexpensively in 5 metre spools.
The substrate would be black flourite (or black flourite sand) mixed 50/50 with small grain inert black gravel. The entire bottom would be densely planted, with the likes of large Swordplants, Giant Vallisneria, and a foreground of Dwarf Hairgrass, (temperature range permitting). I may plant the rear wall as well, in case I don't opt for the 3D background which seems a bit pricey. And I'd have branching vertical tree roots extending down through the entire tank depth if I can find a decent source for such wood. I intend to dose liquid fertilizer as necessary, but I'm hoping I can get away without having to dose root tabs at all once the fish and the tank bed is well established.
As for fish I'd intend to start with 12-18 juvenile captive bred natural colour discus some of which I'd sell off as necessary as they grow, perhaps 10-15 Congo Tetras, a few African Butterflyfish, a group of Rams or Bolivian Rams, several Synodontis Angelicus or as shoal of Panda Corys or Brochis, and numerous Bristlenose and Siamese Algae Eaters. For the discus's initial 9 month grow-out period I'm considering possibly holding off on the Tetras, Rams, and Butterflyfish to be able to concentrate on being able to feed the discus heavily without compromising on water quality. I could feed once or twice a day with frozen food, though I may avoid beefheart if it causes water problems, but I could set up an automatic feeder for additional dry feedings during the day. For temperature I'd target 82 degrees to try to balance the discus's requirements with the upper limit for the other species and the plants.
As a kid I'd kept, bred, and reared mainly South American Cichlids, despite the customary sub-par set-ups of a decade or two ago, and with regular weekly water changes. However, the more I look into it now the more I've been discovering that throwing out all the perfectly good well-conditioned water seems altogether unnecessary. Currently I'm running a small test tank with which I'm trying out some of these ideas and to see if I can maintain stable high water quality with 2-3X overstocked tank, a canister filter for a tank 15x larger, and generous feedings, albeit with dosing with Excel for now. That's still in early stages and I'm still modifying the set-up, but water conditions seem great so far with limited algae (after I added phosphate absorber to the filter).
For the benefit of my fish and to reduce their stress (as well as to minimize the triggers for algae growth, the primary goal with water chemistry would be to achieve balanced stability, (to which water changes would actually be detrimental). With a biological filtration volume of the size I'm proposing, I believe that even with moderate stockings and generous feedings, Ammonia and Nitrites should stay near zero. With dense planting and moderate supplemental CO2, dosing liquid fertilizer occasionally, and medium-high lighting levels, I believe the plants should be able to absorb all the Nitrates (or the ammonia directly which is what plants actually prefer), and possibly all the Phosphates as well. I'd have to carefully monitor Nitrate and Phosphate levels at first, and possibly add a Denitrator filter or Denitrate blocks, and Phosphate Absorber to the canister filter should that prove necessary.
The automated CO2 system would be able to maintain the Ph at a fixed acidity, (although it may prove necessary to add a small bag of gasp! crushed coral to the filter which would dissolve slowly enough to react appropriately with and neutralize the organic acids and carbonic acid produced, thereby preventing the Ph from dropping too far while nevertheless fixing the GH and KH at the desirable soft level for discus.
I would also maintain some fast growing floating plants, which I could easily net out as necessary in order to be able to easily take some nutrients back out of the tank, so while this is still not a closed-system, it should basically equate to food and light in/plants out. And I could control the floating plant quantity in order to shade the other plants and slow down their growth later on so that I don't have to be trimming them constantly.
I wouldn't introduce the discus until the plants were firmly rooted and growing well, at which point I'd dial down the CO2 to a moderate level due to the high water temperatures discus require with its accompanying lower O2 levels. I'm sure some careful monitoring, and fine-tuning of the set-up will be necessary at first, but firm stability should be achievable in time.
Thus, with Ammonia, Nitrites, Nitrates, and Phosphates well under control, and supplemental trace elements and minerals added as necessary, as far as I'm aware at this stage in my research and unless I've thus far missed something, that should perhaps make water changes pointless, shouldn't it? And if that is the case, then shouldn't I be able to keep discus and the other species very happy and healthy in very stable good water conditions, while being able to feed them appropriately to achieve decent growth, with limited maintenance and minor monitoring required once the tank is well established? Iíve seen some mention of potential build-up of vaguely described dissolved organic compounds in addition to nitrates, as well as the suggestion that discus secrete growth inhibiting hormones. I havenít bottomed out this issue, but surely there must be other ways that this can be taken care of, activated carbon added to the filter weekly? I suppose if it proved absolutely necessary then I could do weekly water changes during the grow-out phase. I could install a separate sump tank underneath, with a plumbed faucet, direct drain, and build a utility sink into the downstairs bathroom as I may do anyway then it might be viable in terms of time if I can simply flick a switch to do so, (but NO gravel vacuuming, especially as the tank bed would be fully covered with plants). What by the way would worst-case scenario be? That I end up with a school of a dozen 2/3 grown discus instead? Not ideal perhaps, but not the end of the world I guess as far as experiments go, and thatíd still look spectacular.
I still need to delve into some of the finer points in water chemistry in greater depth and have ordered some books to do so, but I thought I'd put my plan out to the experienced aquarists in this forum as well. I have some time to plan out my tank set-up still, as I'm just now about to embark upon remodeling and extending the living room which will eventually house this display tank, and would appreciate your informed opinions and experience meanwhile. In any case, I'm not looking to breed discus, which I don't really have the time to attend to anyway, I'm just looking to be able to achieve a beautiful natural tank with beautiful fish which I can enjoy without excessive hassle, which to me seems a perfectly reasonable goal to try and attain. Pending success, I may later on also try a similar approach with a small-mid-size marine tank with a trickle filter sump in which I'd be cultivating live rock and Caulerpa algae.