V. sing the Python Products’ No Spill Clean and Fill

No, we are not talking about a snake. This device is the best, or perhaps the worst, device available as an enabler of MTS (multi-tank syndrome). I confess to being a long-term sufferer of this syndrome. My first setup was two tanks, one above the other on one stand. So unlike most hobbyists, I started out with more than one tank. My addiction was limited however. I could never get past the ~12 tank barrier. Upkeep took too much time and physical effort (I have also always been lazy). Then one day I saw an ad in a hobby magazine… it was all downhill from there.

In this note, I have segregated the technical details and expansions or clarifications into footnotes at the end of the article. Those interested in such can review them and some references as they wish. Those wanting only an overview can stay with the body of the article.

At this writing, I restrict myself to a couple of dozen mid-sized tanks. That is subject to change without notice however. I peaked at over 40. I have this vague urge to idle many of the current tanks and bring the big ones back out. Change is good for me; it avoids boredom and burnout. In my experience, the biggest losses of hobbyists from our ranks come from two causes. It seem to be either from novice frustration and recurring disasters due to lack of knowledge and inappropriate fish, upkeep, and equipment, or alternately, from boredom and burn-out from successful but no longer challenging tanks – which still require routine care. I lucked out of the first case by good equipment and advice (available even in those dark ages). I avoid the second by radically changing the way I keep fish, the tanks I use, and the nature of the fish that I keep every decade or so, with a big plus or minus attached to that decade span, and a lot of overlap between “phases”.

Things I do not change radically are some of the basic techniques of water management and tank upkeep. Over a very long span of tank keeping, my general handling of water has evolved to its current status, and that works for me regardless of what size of tanks or what sort of water I am using. The details of my handling might not work best for you; personal preferences are valid and real. What I find straightforward might be convoluted for you, or vise versa. One of my basic techniques is not carrying buckets. Once past the first tank, or with the single tank of 20 gallons or more, buckets are utility devices for periodic but not chronic and continual use for me. I am a strong believe in water partials. I do believe that the answer to pollution is dilution. Water recycles. I help it along.

I do water changes by means of the Python (1, 2). I can either just remove water – in which case I replace the gravel vacuum attachment with a sponge prefilter (3). With a prefilter, I do not have to avoid sucking up shrimp or small fish because they cannot get through the sponge. Or I may vacuum cautiously among the plants of a planted tank – sometimes with the gravel vacuum attachment, sometimes with a section of hard tubing, sometimes just with the bare flexible tubing end. Usually such variant vacuuming is done with the near-end shut-off valve partially closed to reduce – to slow – the water flow. Sometimes I have an appropriate length of gravel vacuum in place, the flow full open if the tank is standard gravel, and deeply (full depth) vacuum the gravel. All of those are valid variations of routine partialling of my tanks. Some variants are used more in planted tanks (less full-depth vacuuming), and others more in FO (fish-only) tanks that are full-depth vacuumed routinely.

The Python is not generally used to directly refill my tanks themselves. I age, de-gas, and temper my water, but that is an entirely different topic for another time. The Python can be used for refilling however, and in emergency situations I do. Adjust the water tap to within a few (+/- ~2 degrees F for me) degrees of the tank water temperature. I usually just finger test, but also have a liquid crystal thermometer on the tank room faucet (a bit slow to respond). Or I use small portable electronic thermometers to compare temperatures. These are cheap and small and very portable; I keep a few on hand. Put the open end of the Python back in the tank (where it will not flop out, please) and change the faucet pump from suction to pressure. This shifts the water flow into the tubing and to the tank. Two variants that I have used are either adding the full needed disinfectant neutralizer a.k.a. “conditioner” initially, or just add it while the water is flowing into the tank, holding the gravel vacuum attachment at a shallow angle just at or barely above the water surface to improve aeration as the tank is filled. When you have the volume restored, close the shut-off value near the output end and quickly return to the sink to shift the faucet pump back to drainage. This releases the pressure in the hose. Open the near-hose-end shut-off valve to allow the hose to drain. Do not leave the hose under pressure any longer than you absolutely must. That would be asking for leaks or possible rupture or failure of the hose or connections. I do have quite high water pressure in my house. Use the vacuum to drain the hose while you are re-coiling it for storage such that it is not left holding water.

Vacuuming techniques do vary with substrate particle size (4, 5, and 6). This equipment is designed for standard aquarium gravels. Larger “pea gravels” from many sources are too large to be vacuumed well. That is unfortunate, as those media, coarse, to very coarse gravels (pebbles) allow much food and waste to sift down between those gravel particles – a lose-lose situation. Even reverse flow undergravel filtration is usually insufficient to keep all debris out of such substrates. Sands have the opposite problem – the substrate itself may be sucked out by the Python – but this can be somewhat controlled by varying the flow rate and angle of the “gravel” washer against the substrate (7). With standard to small gravels and the coarsest sands, the processes are simple.

Light surface vacuuming means just that – move the open end of the gravel vacuum attachment smoothly just over the surface of the substrate, with the gravel vacuum perpendicular (vertical) to the substrate. This will allow the capture of bits of uneaten food, fish waste, smallish plant debris, etc. without disturbing the denser substrate grains themselves. A variant of this lightest vacuuming technique is to just lightly vacuum the surface layer of the substrate, going into the gravel physically with the vacuum attachment only a quarter to half an inch, and lifting it back up. This still-light vacuuming will get more and smaller particles out of the gravel before they are fully digested. Remember that this is real removal of material, before full digestion, breakdown, or mineralization, so is more beneficial to water quality upkeep than simple filtration alone can be. The materials are being directly and immediately removed from the system, not just stored in the filter for later removal by the hobbyist/keeper.

Deeper and full-depth vacuuming are larger-scale procedures. Here the gravel vacuum attachment is pushed deeply into the substrate, all the way to the bottom of the tank. The tube is pushed down as far as desired, paused very briefly, and then lifted slowly back to and above the gravel surface. That action will tumble the gravel grains in the tube by the water flow and allow entrapped mulm (8) to be sucked up and out by the water flow, while the gravel itself falls back to the floor of the tank. If this has not been done for a significant period, or never, the brown cloud being released into the outflow may gross you out. But if done regularly and routinely, while still cloudy, it is not horrible. Deep vacuuming on a routine basis does help significantly reduce the usual increases in TDS (total dissolved solids) seen in tank water versus make-up water. The technique, like frequent rinsing of mechanical-only filters, gets materials out of the tank before they are fully digested and mineralized. Even if the material is fully mineralized, not all of the soluble minerals involved will have been dissolved so that vacuuming and removing this material reduces and helps control the levels organic and inorganic build-up in the water column.

Slightly off-topic but still applicable, this might a good place to make a plea for no more substrate than is needed for the tank. A deep substrate can serve as a reservoir for many materials (deep unplanted substrates are great nitrate reservoirs, among other things). Due to decreasing oxygenation with depth (9), I see no benefit from having substrates deeper than is actually required. Unplanted tanks rarely need deep substrates at all. Heavily planted and aquascaped tanks may use quite deep substrates in large tanks, but plant roots do modify the conditions in such substrates. Roots both absorb materials from the substrate and bring oxygen down into the depths of the substrate to support their own processes. Not enough oxygen is released in the substrate to really aerate it, but there is some positive effect. If you do not need a deep substrate, you are very likely to find your water quality better or easier to maintain with a shallower substrate. Planted tanks are handled somewhat differently than fish-only tanks. That process is discussed in more detail in other articles.

Whatever style or type of tank you keep, the Python can be a valuable and time and labor saving device for you. My original unit is well over twenty years old at this writing (since shortly after they came on the market) and still going strong. I admit that I have replaced the faucet pump more than once (mine are still the plastic ones), but usually because I have crushed too many snail shells inside the base flow diverter and damaged that more than the top threads. My unit does stay in place on the tank room laundry tub, so thread issues are unlikely. I also replace the hose washers periodically, just as I do on outdoor hoses. I do not want or need any leaks on my floors. I can make enough spills and messes on my own; I do not need mechanical help to do that. Overall, the Python is one of the best and long-term cheapest tank accessories I have purchased, as mine is used almost daily.


1. The Python device and its components: For pictures and drawings of the components of the system and the assembly in position for use, see:


The at-faucet assembly shown has some optional components that you may or may not elect to use, personal option and individual needs again. The primary component is the (green) plastic faucet pump (part 13-B on the referenced page). This is the key component, a simple venturi device. The lower, bell-shaped part of it is pictured in the lowered, suction (vacuuming) position – this function is discussed in footnote 2, below. It can be lifted and twisted to secure in the upper position and will then divert water away from the flow-through-to-drain lower position to instead send water through the hose to the tank. The hose is flexible and clear. It includes a shut-off valve near the distant end. The end of the hose is fitted with a gravel washing tube of larger diameter for routine vacuuming operations. Alternate longer gravel vacuum tubes are available as well.

2. How the Python works: The operation of the Python is an application of the venturi effect. It is a remarkably simple device. I will not give a physics lecture here, but refer you to Wikipedia:


The company says that this device uses one gallon of tap water for each seven gallons of tank water removed. I will accept that for tanks whose water level is approximately equal to the level of the pump on the tap, with some minor effects from the length of the tubing used. Overcoming friction does require work, so I would expect long tubes to be slightly less efficient than shorter ones, so those would require a bit more tap water.

For tanks higher than the tap, the tap may be shut off and the device will operate as a conventional siphon hose after starting by use of the tap. This gravity and air pressure operation will not be as fast as with the water tap running, but it works. With the tap on to increase suction and the rate of water removal, I would expect the efficiency to be better than that stated by the company.

It the tank’s water level is below that of the tap pump, I would bet on significantly lower efficiency than that given by the company. The device must both overcome friction in the tube plus lift the water to the level of the device on the tap, two separate work operations. But it does allow me to operate tanks on or near the floor. I am willing to pay for that increase spatial efficiency (I can use more of the tank room volume for tanks) with some increase in water use.

Warning note from personal experience: I have unusually high tap water pressure in my home (~100+ psi). For Python use, this should give me quite good operation. But, the unit operated very poorly on modern, flow-restricted faucets. As I use a laundry tub (no flow restriction) ordinarily, this has not been a problem. But I ran some tests and found that my bathroom and even kitchen sinks do not give good results with this device due to their flow restrictions.

3. Prefilter sponges: I use the Lustar FilterMax line of prefilters for any tank with shrimp breeding or fish fry if I am not gravel vacuuming. These have two porosities and two sizes of the finer porosity available. These prefilters come with an assortment of hard plastic adapters for filter intakes and flexible tubing, one of which is a perfect fit with the Python tubing. I just remove the gravel vacuum attachment from the hose and replace it with the prefilter assembly. I suit the porosity and size of the sponge to be used to particular job to be done. This technique is used primarily in tanks with fry or small shrimp, or in my moderately to heavily planted tanks where I am doing partials without the need to do much vacuuming.

4. Substrate particle size: The substrates used in tanks vary widely in particle size and distribution. There are multiple grade scales used commercially. For simplicity and ease of reference, I would suggest using the size definitions as given on Wikipedia:

http://en.wikipedia.org/wiki/Particle_s … in_size%29

5. A significant factor is the range of sizes in a particular substrate. Only commercial aquarium gravels are likely to have a fairly tight spread of particle sizes, plus a small percentage of “fines” (much smaller particles abraded from the standard size for that gravel). Loss of the fines in initial rinsing is trivial. But those fine particles may not be good for your plumbing. Capture of fines in a bucket for other disposal is good. In the tank in operation, those fines are more likely to be sucked out and to the drain as well. Mixed substrates (standard gravel and sand, or pebbles and sand) present the biggest challenge to the keeper during vacuuming. Suction strong enough to tumble and thus clean the larger particles may be enough to remove the smaller sized material. Lower suction (from lower water flow – controlled by the near-end in-line valve) may not adequately tumble the larger particles.

6. Another factor with mixed-bed substrates is long-term particle size assortment. Over time, the smallest particles in the substrate tend to migrate downward between the larger particles. If you set the tank initially with a medium gravel and cap this with a medium to fine sand, that is a temporary arrangement. With time the tank will have a sand base with the gravel above it. It is the nature of the materials. Smaller particles migrate down through fields of larger particles over time. Don’t try to fool Mother Nature – she has the rules on her side.

A side note on sizes and appearance: Uniform particle size and color tends to look unnatural to me. It is not what is usually seen in the wild. If you use a smallish range of sizes (and perhaps shades or closely related colors), or if the gravel or sand chosen has a less-than-tight size range, we are more likely to see the setup as natural in appearance. That sort of material selection is also more likely to maintain its appearance over time, despite fish disturbance and keeper vacuuming. When the particles sizes are fairly close without tight uniformity, the natural downward migration of the smallest particles is less effective than when there are wide gaps between small and large grain sizes used.

7. A quirk learned in the lab: Sliding friction for smallish particles in a liquid medium is more effective than free-fall in the column of that liquid. Sand particles in water suspension will return to the tank substrate – where you want them – better and faster with the gravel vacuum tube angled. They need free-fall only the shorter distance to the tube wall, then to slide down the tube surface to return to the tank. It works.

8. “Mulm” is the final breakdown product of fish/shrimp/snail waste, uneaten food, plant debris, dead bacteria and infusoria, etc. up to dead fish if not removed. At its end point it is inorganic, fully mineralized. At intermediate stages it has variable organic content. The appearance of mulm is brown and the particle size is quite small (clay-like rather than sand-like). This is what we are vacuuming out when we vacuum the substrate. The early stages are what we see when we rinse mechanical filter media frequently. Mulm is the fine haze that we stir up when we rearrange the décor or replant live plants. In planted tanks, some mulm is valuable. Fully mineralized means in part that the nutrients involved are more easily accessible to the plant roots, so mulm is desirable up to a point in planted tanks. Even in planted tanks, too much is still too much. So we do refresh (vacuum) the substrate periodically, just not nearly as often as in FO tanks. In FO tanks, it means that those same materials are more soluble in the water column. Since in FO where they are not needed in either the substrate or the water column, they are better removed.

9. Below the very top grain layers, oxygen and other materials depend on diffusion and Brownian Motion (10) to move through the substrate. Other than in pressurized flow (as from UG – undergravel filtration, or RFUG – reverse-flow undergravel filtration), any currents are damped out by the close fit of the substrate grains. The slope of the oxygen depletion curve is always negative – decreasing O2 concentrations with increasing depth – but the steepness of that slope depends on particle size. Taking commercial aquarium gravels as the standard, smaller-grained gravel would have a steeper slope, would decrease O2 levels faster with increasing depth. Coarse sand would be steeper still, and fine sand or sugar sand will have the steepest slope beyond that of clay mud.

10.“Brownian Motion” refers to the random motion of molecules. More information and some of the math may be found in Wikipedia:


This article has been edited for this site, Sept 2010.

Robert T. Ricketts, a.k.a RTR

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Robert T. Ricketts

Retired research scientist (biochemistry and physiology, pharmaceutical development) and senior process analyst. Started fishkeeping in the dark ages (1950s), first SW tanks in the mid-60s, first puffers in the early 60s. Started with two tanks and never less than multi-tanked excepting some periods in college and grad school. Specialty if any would be filtration and water management. Primarily species tanks, planted whenever possible/practical and some where it not really practical. Ran something on the order of >150 tank-years* in studying optimum tank conditions for F-8 puffers, the largest tank study I have done. Other studies have been significantly less. Alternate canister use was mid-40s, OERFUG just over 60, veggie filters only about 25 to publication, but still going on less intently. If it had been known that the F-8s would live so long, it probably would not have been started at all. *One tank-year is one tank for one year.