28 replies to this topic

[WheelsOC]

I think I'm finally doing it! Wanna turn a 110 gallon oval poly stock tank from Tractor Supply Co. into an outdoor aquarium. These are pretty typical container pond project fodder; recyled LDPE plastic tanks designed for holding huge amounts of water while standing up to direct sunlight all day. This one is 20 inches tall from the ground, little over four feet wide and three feet front-to-back. I hear TSC cycles through various suppliers of tanks in the same basic pattern every few years so if you see one that doesn't look EXACTLY like this, don't worry about it.

I've been pondering this project for a while, and here are my ideas so far.

 

 

Location, Climate, Locals

Newly acquired stock tank just getting rinsed off in its approximate final location:

 

It'll be on the back patio, front facing roughly south. The property is surrounded by tall old hickory, tulip trees, and oaks on all sides, and this is the most consistently sunny location at the house. I live in upstate South Carolina, which is a little more temperate than the midlands or low country in terms of climate. That just means we get long-sleeves weather for about a month and light snow flurries once or twice from January through March, but we still have "summer" temperatures for basically 5 months out of the year. Fish don't care about the humidity like the rest of us, but we have had a long string of 90+ degree Fahrenheit weeks this last summer that drove the heat index well into the 110s. Wildlife in the yard consists largely of insects, chipmunks, frequently some whitetail will wander through and chew up some greenery, some semi-feral neighborhood cats, and we have a lot of tree frogs and toads when the weather is warm and humid.

I've left the tank out for a few rainy days and it can accumulate roughly 6 inches of water on 2 inches of rainfall. So to deal with overflow, I'd probably drill a series of small holes just below the rim on the back wall of the tank. I'd make them small so they don't risk sucking out any fish. I've seen how to make a passive overflow siphon out of PVC pipe, but I don't know how reliable they are over the long-term with water loss from evaporation, etc. breaking the siphon when it's not actively running.

My original goal for the aquascaping was one of those slackwater, soil-substrate, heavily-planted Walstad type natural ponds, with minimal filtration and elaborations. But after carefully examining the solar situation back in June (when many of these photos were taken), in nearly optimal conditions, I don't think it gets enough direct light for deep pond plants. Too many 80-foot trees around the property. Some part of this tank is in shade except for the middle two hours of the day, and the high walls shade the front of it down to the floor.  The picture above was taken around 1:30 local time and the sun was already creeping behind the canopy and casting a shadow on the western side of the tank.

So my next idea: a stream setup. Not strictly biotope, but something with some constant flow, pebbly substrate, few to no submerged plants. I wanted to divide it into a front and back part with a sheet of clear acrylic and have water circulating pumps at opposite corners to keep the flow going around the perimeter; say, one circulating fan in the front right and another at the back left, obviously pointing in opposite directions. The divider would probably be offset towards the front of the tank rather than directly centered. I plan to rig up a frame from PVC pipe to keep it standing upright, and weighted down with the planter in back of the tank. With a narrower space in the front and a wider lane in the rear, it should provide some variation in flow rates so fish can choose where to park themselves.

 

The Tank and Layout

I mocked up a layout with a 24-inch planter box for the back rim of the tank for some emergent plantings, and an old chunk of wood laid approximately where I'd put the tall divider to separate front and back flow areas.



Side view, front/south side to the right:



So the internal divider would run about where that plank is. The PVC frame for the divider would also form a stand to hold up the planter box. I plan to let the planter at least come up above the waterline, just in case some frogs find their way into the tank and need a way to get back out.

I'd also like to try and cut out a window in front so that the fish can be seen from side-on. This is actually pretty tricky; both the LPDE of the tank and the acrylic panels are notoriously bad at sticking to anything, so just running a bead of silicone to seal the viewing window would be a non-starter.

 

I've seen some aquaponics setups and kits with similar plastic tubs where a window cutout can be sealed by sandwiching a neoprene gasket between the acrylic window and the tank walls, which is what I plan to try. I've got a couple of acrylic sheets cut down to 18 x 18 inches, and a piece of neoprene sheet (just came in the mail yesterday, still got that factory stink on it!) that I can do likewise. My thinking is that a 15 x 15 inch window cutout will allow enough room to see the fish, while leaving a 1.5" overlap with the gasket and acrylic sheet. 0.75" in from the edge of that, or basically all around the middle of the overlap, I'd drill some holes for stainless steel bolts with rubber washers and a little just-in-case silicone caulk to tightly clamp the acrylic panel in place, hopefully avoiding leaks.

Here's the acrylic window panel leaning against the inside wall of the tank to give a sense of scale:



So the actual window cutout would be even smaller.

 

 

Filtration

Since I probably can't rely on sheer lush plant growth to soak up those nitrogen wastes, I wanted to do a powerhead or pump with a big sponge pre-filter on the intake and to run it through containers of lava rock for biological filtration. In fact I was going to try and see about working the whole thing into a DIY cascading fountain off to one side of the tank. The water would be piped out of the tank and through the pump up into some sort of basin full of lava rock (the pump outlet would have some sponge, pot scrubber, or a mesh basket of polyfill around for mechanical filtration, of course). Then it would flow through a pile of lava rock until it cascaded out of the basin, down to a mid-level basin full of more lava rock, down to a final basin also full of lava rock and maybe a few potted plants until it drains back into the pond. Here's my concept sketch to capture the essential elements:

 

 

That fountain idea may be too ambitious, though. I could always just use a regular canister filter, I'm just trying to come up with a decorative way to incorporate it. Combination waterfalls/filters are popular for ponds, but I've never seen someone try to make it a legit fountain.

 

Livestock

In terms of flora, I'm trying to stick to stuff that's native to the continental US (and even better if it's found in my home state of SC). Again, not strictly going for a biotope setup but I'd get more out of it if I could stick with native plants for a native tank. I think the only submerged plants that might work would be some Fissidens fontanis on the hardscape. Pretty sure we get too hot in the summers for willowmoss to thrive, but I'd be glad to hear otherwise.
For the planter, which I'm going to open up with some drilled holes for water flow, I'll try to have some potting soil contained in some pond planting bags. Locally, I've seen a lot of "willow primose" (probably Ludwigia) growing in some streams and creeks. I'd love to have some Lobelia cardinal flower growing in the planter, and even some Sagittaria latifolia if that's possible. I've also seen a lot of Podostemum ceratophyllum in a river the next county over, but I hear that's difficult to grow in captivity. And if all else fails, I'm sure a few dense tufts of hair algae will be willing to help out.

In terms of fauna, I'm leaning towards minnows instead of centrarchids. I'm one of those weirdo schooling fish fans, the kind who would rather have 3 dozen small tetras or danios in a tank than 2-3 big cichlids. So I'm looking to house a couple of Nocomis chubs and a big school of Notropis, probably the yellowfins I seem to see everywhere I dip my camera. I wouldn't be averse to another minnow species, maybe even some showy Rosy Reds from the pet shop feeder tank if they like as much current as the chubs and shiners do. If so, I can throw in a few small terracotta pots and bricks for them to take up in. Heretical as it may sound, I'm not really thinking of darters for this tank. But maybe some native aquatic snails (bladder snails? do pond snails tolerate current?), which should serve as both a cleanup crew and their spawn, a food source for hungry fish.

 

Speaking of which, live foods will probably have to be skyfall-sourced only. I'm not up to rearing worms and larva for the fish, hence my reluctance to include the darters.

 

 

Summary

 

So what I'm thinking is a windowed stock tank with a strong, circulating current; an internal divider to keep the flows separate; some sparse emergent planting, maybe some mossy rocks or wood decorations; pebble substrate; a more or less fancy pumped lava rock filter; some local minnows to stock it with.

It's gotten pretty late in the year, so I anticipate not having everything set up and settled in this season; may have to pick this back up in the spring before adding fish. That'll also give me a chance to see how cold the actual water gets and how well my setup would work in the winter before committing any livestock to the project.

I've never done something like this before. Any tips, insights, suggestions, thoughts on why it won't work? Or another question: am I just massively overthinking this whole thing?

[littlen]

There is a lot to digest in your plan, but it sounds exciting.  The one thing I'd like to jump right into is your LSS/filtration idea.

Pumps do just that,..."pump", or push water.  They only inadvertently 'suck'.  You'll need to put the pump in the stock tank and have it push the water to the highest basin.  Or if it is an external pump...add a bulkhead to the sidewall of the tank where the yellow plug is on the first picture, and plumb it just outside of the tank.  It can also push water to the top from there.  You can put a valve on the discharge side of the pump to slow your waterfall if you so desire.

 

 

You may want to consider what the high temps will end up being for your tank in the middle of summer since it will be exposed like that.  Remember that in addition to the 100F+ air, and being recirculated by a pump, the entire body of water will be the same temperature.  There will not be any thermoclines at the bottom for the fish to take refuge in.  Then you can see which inhabitants will be able to tolerate said temps.

 

Good luck.

[fritz]

This sounds very interesting and we would like you to consider writing something up for American Currents.  It could even be a two-parter:  Planning as you have here and Final Project when completed and operational.

[Chasmodes]

Cool concept.  I agree with Nick about the pump.  If it's not a primary source of flow, then you don't need an expensive one, and the head pressure, I assume, probably would be less than 6'.  I'd go with an internal pump, it's easy, and put it behind your barrier out of sight, that is, if you have to purchase one.  But with the outside plumbed external pump, I think it would work but it would be exposed to the elements, that's why I'd go with an internal pump.

 

You could supplement falling food with an automatic feeder that can clamp on the side of your tank and use flakes and/or Vibra Bites.  Greenside darters will eat the Vibra Bites, and my fantails do too, that is, if you wish to add darters later. They will learn to eat them when they get hungry enough.

 

For hot summer months, you could set up a canopy tent like thing for longer periods of shade.  How hot does it get in the shade where you live?  Another option would be just to do water changes daily with your hose and let your water fall pump discharge the warmer water.  Even better if you could develop a automatic water top off system, then increase so there is an exchange of water and a calming of temperatures.  You could create an outflow off your plumbing to the top of the waterfall with a T'd line and ball valve, to divert some flow.  Lot's of options...

[Peixe11]

I would suggest putting some kind of cover over it. I left my stock tanks for fish breeding uncovered last summer and found 2 drowned squirrels. Put netting over them this summer and found a dead rat. I'm not sure what I will do next summer, maybe dig a moat as well?

The acrylic window looks really cool! Def post pictures once you have it up and running.

[Michael Wolfe]

I am in a climate not too different from you (Athens, GA).  And I would warn you to be very careful about temperature.  My experience was that all the slack water stuff does very well.  But when I tried to add flow or circulation, it ended up homogenizing the temperature and of course the temp in shallow water or at the surface of the water can be quite hot in the summer.  In my case, circulation ended up raising the temperature of the stock tank to over 80 degrees and killed all my stream fish.

 

You may have a different micro-climate, like maybe I had too much sunlight and you really have a lot of shade.  But I thought I would at least share my experience as a watch out.

[WheelsOC]

I'm not making any headway on the elaborate fountain/filter idea (and worrying over it has been holding everything else up) so I may instead go with something more conventional like a regular canister or filtering pond spillway. If even that is too much mixing, I guess the best thing for it is just plain ol' sponge filters?

 

A lot of great advice so far. The temperature warning concerns me the most, especially since it's these stream-loving minnows I really want to try keeping at the moment. It would be very ironic if the very lack of insolation which pushed me in the direction of a sparsely-planted stream tank wasn't enough to keep the water tolerable for stream fish! As I said, the patio doesn't get many hours of complete sun even in high summer. By 2-3pm in June it's pretty much completely shaded. Some more pictures on a sunny day to illustrate the situation: 1:23pm on June 1st, 2:17pm the next day. It's still a sunny day in the second picture.

I've seen more than one fishkeeper post their DIY chiller designs where they simply run water from their tanks into a coil of tubes stuffed into a mini-fridge. Here's the most recent example. The builder says he can cool the water in a 55 gallon by 10F over a few days and maintain it in a 125g tank at 68F if ambient is 70F or so. Even a design like that may not be up to the task, so I probably shouldn't count on adding a chiller to the project.

All this is theoretical at the moment, so I'm going to have to get a full tub and get some measurements first. Especially while we still have a few more warm days on the calendar.

 

This sounds very interesting and we would like you to consider writing something up for American Currents.  It could even be a two-parter:  Planning as you have here and Final Project when completed and operational.

Well thanks! Glad to know it's an interesting problem I've set up for myself, but first let's see if I can get this pond off the ground!

[Michael Wolfe]

A couple of more cooling thoughts:

• I saw your one tank sitting on concrete and wonder if sitting it on (or even a couple of inches down in) the ground would be a better idea.  I have always sat mine on the ground directly and used no circulation (letting a natural temperature gradient develop with no circulation at all).
• Your talk of coolers has made me think of maybe some sort of geothermal cooling... maybe even something as simple as a coil of hose buried in the ground? I mean its not like we are up north, you and I.  Bury it 8 inches deep and you would have 55 degree temps year round and no real chance of freezing.  I dont know if anyone has ever tried that, but it seems like it would work easier and nearly free? 

[littlen]

The mag-drive pumps are typically used in an in-tank manner, but can be plumbed externally.  I'm sure it would be a wash in your warm climate, but an in-tank pump will contribute to heating your tank.  I would encourage trying to keep some sort of waterfall feature.  The falling water will have some evaporative cooling effect---which might also be a wash.

 mag drive.jpg   236.99KB   0 downloads

 

The more you can dig your pond into the ground, as Michael suggested, will help keep it cooler.  I think your current setup might be troublesome in the long run trying to maintain stream species.

[Chasmodes]

Also, adding to Nick's point the powerheads that produce your flow can contribute heat.

[WheelsOC]

Digging is a no-go, unfortunately. Various reasons, but perhaps one of the most important (to me) is that I'd like to keep my viewing window if at all possible, instead of futzing with a periscope or using my camera to get a closer look at the fish.

 

I've thought about dry-stacking some landscaping bricks (the kind for garden borders or low retaining walls) in front of the tank and around the sides for purely aesthetic reasons, don't know if that would help the temps by shading the front of the tank or hurt by having all that masonry soak up the heat during the daylight hours. Thermal mass can be a blessing or a curse!

So thinking about the heat issue, Instead of cement brick I would probably use those stackable cement planter wall blocks to hold some 2x6 direct-contact rated boards to make a quick wooden facade around the tank. I could even slip some foam insulation board behind it. As long as I can leave a gap in front for the viewing window.
Raising the tank up wouldn't be too much trouble if I can just slip in direct-contact lumber underneath it. I presume leaving a few empty spaces between the wood should help with air flow under the tank. Cement flagstones or tiles would be stronger, but also would be better at conducting heat between the patio and the bottom of the tank.
That should limit the amount of radiant and conductive heat the tank would have to deal with from five sides, leaving mainly direct sunlight from above and the ambient air temperature to deal with.

The next week is projected to only be in the high 70s, but I'm going to fill up the tank and monitor the temperature anyway. Thanks for bringing this to my attention, it's really changing the way I'm thinking about this whole project. There's no point in having a pretty pond if it's going to stress the fish to death!

[WheelsOC]

As of this morning I have the tank mostly filled (we're expecting rain this week, like most of the Southeast) and I have a small old Petco 160gph-rated powerhead in there just to churn up the water a bit. I'll let the temps stabilize for a couple of days and then I'll starting comparing tank to ambient. Unfortunately September decided to NOT be a summer month around the equinox, so I'm not sure how many representative hot days we'll have before it's full-on autumn.

The reason I took my time filling up the whole tank is because we're on a drilled well and I didn't want to tax anything by doing the whole 100-ish gallons at once, so I spread it out over a couple of evenings before turning in at night, and let everything recharge overnight when nobody's using water in the house. Just because we've had various issues with our well in the past and I'm ultra-conservative about it these days. On the plus side, the water (when filtered for sediments) is naturally delicious and soft. Virtually no carbonates to build up, no detectable lead, no algal blooms to deal with, and no chlorination to neutralize. A lot of iron, but that just goes with the geography.

Also, this has been instructive in another respect. The included suction cups for my tank thermometers and powerheads? Useless. I don't think the surface of the LDPE is smooth enough for them to seal properly, so I'll have to use some mounting clips on anything I put in.

So while I'm letting the temperatures write their story, I'm going to focus on the hardware for that viewing window cutout. My idea is to have the tank side wall cut out significantly smaller than the acrylic panel, cut my neoprene gasket sheet, and sandwich them together with bolts and nuts securing double-layered rubber and steel washers inside and out. Again, because common sealants don't adhere to either LDPE or acrylic, I can't just caulk it up and expect it not to leak. My plan is to use all stainless steel hardware, bolts and nuts cut to 1/4"-20 size, fender washers with a 1/4" inner diameter and 1-1/4" outer diameter, and neoprene washers with the same OD but 3/16" ID to really grip the bolt tightly and help seal it.



So my mounting order is going to be, from inside to outside, bolt -> steel washer -> neoprene washer -> acrylic sheet -> neo. gasket -> tank wall -> neo. washer -> steel washer -> nut. I might even try dipping the bolts in Plasti-Dip (which is fish-safe when cured) to really seal up their threads as I install them.

[Chasmodes]

I guess you won't know about leaks until you try and test it.  If, after testing, it needs more, maybe make an acrylic frame to adhere to on the outside, or maybe wood painted with Drylok, to give your bolts something more solid to seat into?

[WheelsOC]

I think the bolts will be okay. All else fails I can try blobs of silicone on the bolts and just live with the permanence that entails. It's mostly the issue of water wicking under the gasket materials that'll likely be a problem.

Heh, when I bought this stock tank the idea was to just have a low-maintenance Walstad jungle tub as a simpler alternative to a high-tech indoor aquarium. Now I'm down to specc'ing specific stainless steel alloy flange bolts on McMaster Carr because most local places only have zinc-plated, or not the size I'd like. Nothing like a DIY project to induce a little Scope Creep!

Probably won't be any updates over the next week just for lack of stuff to get done. Hope everyone stays safe in the meanwhile.
 

[Chasmodes]

Yeah, that's so true...for every inexpensive build or DIY idea, it always turns out more expensive than if I just were to buy an all in one set up LOL.

[WheelsOC]

Minor update:
Still waiting on hardware to be delivered before I can install the viewing window. I also have some pre-molded 2.5 gallon "streamlet" waterfall basins due in a couple of weeks to start building the waterfall filter. Still going with a 2 or 3 tier design, with each basin full of lava rock. I'll use a pond pump in the pond itself and pipe water up to an outlet covered with some kind of mechanical filter in the first/highest basin.

The weather hasn't hit another "summer" pocket yet, so air temps are still in the mid-to-low 70s Fahrenheit by late afternoon. Checking the water temperature irregularly but frequently each day at different points. As measured by, like, 3 different thermometers the water in my stock tank has barely risen to 62F at the warmest and is staying around 50-58 most of the time. I have the good ol' floating aquarium thermometer, a new sinking pool thermometer, and a no-contact IR thermometer. They all give readings within about a degree compared to the others so there doesn't seem to be any relevant temperature gradient with the powerhead churning things up. Also, over the past week the water level has dropped about an inch through evaporation despite a brief shower on day 3. I'm documenting the temperatures with timestamped photos so what I should really do is throw them all into a spreadsheet at some point.
Still hoping for a week or two of high temps again to see how the water reacts.

 

I adopted a few resilient plants from a local lakebed. Where I took them, the water would normally be clear as literal mud and about a meter deep, but pool has been low lately so they've had the opportunity to sprout up. Picked up several Sagittaria latifolila, all about 3-5 inches tall so far; one clump of some kind of Eleocharis spp.; and a few Cool Whip tubs full of terrestrial moss divots kicked up by the deer in our field that were otherwise just going to dry up in the sun. I'm no plantologist or anything but I hope to keep them alive until I get the pond situated and can plant them in hanging/floating planters.



I kept some clumps of the lake bed silt around their roots and carried them in a lined box set in a plastic shopping bag to try and keep from drying their roots out or bashing their stems too much in transport, but the whole trip was still on foot and therefore a little bumpy. I left the silt around their roots as I transplanted them into containers full of soaked potting soil. One little Sagittaria is staying in its own mud clump, but surrounded by the moss patches instead of being properly potted up as an experiment.
They look a little beaten up, but we'll see how they do. Arrowhead is just about my favorite sub/emergent plant so I'm glad I was able to find some volunteering in a precarious spot to rescue.

Gonna be a while before any more progress reports. The next biggest hurdle will be putting in and troubleshooting the viewing window, and then test-fitting the cascade filters.

[gzeiger]

I have a stock tank like this that's packed with emergent plants. Sagittaria is a great choice, and you can eat it when you thin them in the winter. I also have Acorus calamus and some Asian water chestnuts (Eleocharis dulcis, not Trapa natans). Lotus might also be a reasonable choice. Sagittaria and Nelumbo can provide enough shade to affect water temperature, although the latter needs root space and is hard to manage in pots. I would definitely at least paint your tank white in that climate, or shade it as you suggested with blocks. Thermal inertia isn't necessarily a bad thing to dampen the day/night swings and lower the daytime high, plus blocks will radiate a lot of heat outward away from the tank, and much of what is dissipated toward the tank will be carried away by convection currents. I think you'll get a lot of value from that. 

[WheelsOC]

Winter has definitively left us behind, so it's time to revive this project!

I've changed some details but will still mostly stick to my sketched layout above; a 110 gallon stock tank pond with a viewing window and some water circulating around the inside, with a pumped waterfall/biological filter feature off to the right-hand side.

I've cut out the window panel for the side of the tank and drilled the bolt holes. Next steps will be to punch holes in a gasket I cut from a sheet of 1/16" neoprene rubber, then drill all 44 holes around the perimeter of an acrylic panel to serve as the viewing window. Cutting and drilling the tank itself was easy, since the LDPE it's made of is quite 'soft' and workable with regular wood-oriented tools and bits. The acrylic is what makes me antsy since it's more brittle. Hopefully, between my tight-fitting rubber washers and gasket, it will all be water-tight without needing any sealants. But I bought some extra GE silicone 1 just in case.



The tank will sit on three of these dolly carts, each one rated to hold 1,000 pounds. They'll all be zip-tied together and the gap between their molded grips will be filled with cut sheets of corrugated plastic. This should help support the bottom of the tank, and providing a little extra insulation from below. The carts will lift it off the paved patio to help regulate the temperature of the tank, and also facilitate any need to move it in the future.

 

Off to one side will be some stands for the cascade feature. While the actual stands are still something I need to sort out, I already have a pond pump and tubing for the cascade; as per the advice up-thread I'll put the pump inside the tank itself and just pipe the water up to the top-most basin, with something to filter the water buried at the end of the pipe (a wad of poly-fill inside a clay pot at the end of the hose could work). The basins will be filled with lava rock chunks, and maybe those potted plants I talked about.



I plan to enclose the whole thing, tank and fountain, with stackable cement blocks that have slots for 2 x 6 planks, the kind used to build up raised garden beds. Between the tank itself and the enclosure, I could put some sheets of insulation foam if need be. Of course, there will be a section open in front. Hopefully this will all result in a pleasant-looking patio water feature, with the all-important front viewing window for greater fish enjoyment.

 

Of all the plants I set aside over the winter, only the spikerush made it through intact and thriving. It's even flowering as we speak! In fact I seem to have acquired another, younger one after the winter break, with no effort on my part (it volunteered from one of the other pots). The original Sagittarias all died back in a matter of weeks. But two small arrowheads revealed themselves about a month ago, either from their tubers left in the pots or from seeds left in the lake bed soil I borrowed. Either way, down to three or four lake bed plants now.
I did manage to grow some common jewelweed (Impatiens capensis) from seeds I snagged out of an exploding pod back in late October. They grew to about three inches since March. Last week I might have given them all transplant shock when moving them to larger individual pots as their leaves are all drooping. Hopefully they pull through, some colorful pollinator-attracting wildflowers would be much appreciated in this project. (I also got some high-speed footage of the pods going off at the time, thanks to my Samsung phone's nifty camera. Pretty cool little seed-flingers!)

 

To plant them all, I've got a self-watering 24" window planter box with the watering tray removed. I've lined with some non-woven landscaping fabric, which is permeable to water (I tested!) but will hopefully contain the finer substrate particles. The planter will sit on a stand made of PVC pipe inside the tank, adjacent to the back wall, and be filled with a substrate to hold the plants. See the mock-up pictures for the general placement.

 

I'm thinking of mixing a little organic potting soil with a few shovelfuls of local creek sand or pool filter sand, a bit of local clay, maybe mixing in a handful of oyster grit for calcium/magnesium supplementation. Our local soil and surface waters are very soft, and deficient in Ca and Mg. I've read that a little extra hardness won't hurt plants that thrive in soft water, it just feeds other plants that out-compete them by fertilizing them with carbonates and removing that as a limiting factor.

I might also add some small terra cotta pots with smaller plants in the waterfall basins as part of the filtration fountain feature. Speaking of which, I have the basin forms for the three-tiered layout! Rather than futz around with specific pots or bowls, I just bought pre-made cascade forms for in-ground ponds.

As for the fish, I'm leaning away from capturing local Notropis and Nocomis since the water circulating in the tank might get too hot in the summer months, as discussed above. How about some sizeable schools of Cyprinella lutrensis and "Rosy Red" Pimephales promelas?  They should be a little hardier to warmer temperatures, right?

[ShadetreeIchthyologist]

I'm thinking of mixing a little organic potting soil with a few shovelfuls of local creek sand or pool filter sand, a bit of local clay, maybe mixing in a handful of oyster grit for calcium/magnesium supplementation.

Would be careful using any sort of potting soil. It could cause lots of nitrate/nitrite problems down the road.

[Chasmodes]

Very cool. It looks like things are coming together nicely. I'm looking forward to your progress. I have a question though...Is this tank going to be only 3 or 4" off the ground, or are you building a stand to go on top of the dolly? I was just wondering how you are going to view the tank. I know from having QT tanks on my basement floor, that, at least at my age, getting on my hands and knees on hard pavement is tough on my knees, and with my eyesight, stuff isn't as easy to observe. Having your set up so that the window is at eye level might be more fun to watch. Nice work! I love the cascading fountain/filtration idea.