I love my water gardens. Particularly the anticipation and reward that comes from discovering that first flower from that new waterlily. Winter here in the New Jersey Skylands is made more tolerable with a pond catalog in hand, and a dream in an armchair of what I will do outside when spring arrives.

But in my heart of hobbyist hearts, I’m a fish guy. A card-carrying member of the organized aquarium hobby. One of those guys who keep dedicated rooms in their basements for breeding fish and CO2-injecting plants, meets once a month in dark veteran halls and nature centers to swap exotic fish, and enjoys rousing discussions on do-it-yourself automatic water changing systems and brine shrimp hatcheries. I enter fish shows and go to aquarium hobby conventions.

Oh yeah, most of us don’t care for goldfish or koi either.

So what am I doing here besides writing an article for WGI’s fine journal (after all, who can ever refuse Kit)? I keep tropical fish outdoors in the summer. That’s what got me into water gardening. And it is a practice overlooked by many “pond plant” folks as a way to enhance your water gardening experience.

Keeping and breeding tropical fish outdoors in the warmer months is a practice as old as the 100-year-old tropical fish hobby itself. It was a quiet, quirky custom until about 10 years ago when the pond craze cycled through here in the US, and folks like me started rediscovering this lost art. I’ve been personally espousing the practice, which I coin “summer tubbin”, in my writings and speaking engagements for a decade. It continues to grow in popularity among aquarium hobbyists, and I think it has brought more of them to appreciate the water garden.

The color that develops in tropical fish raised with such varied foods and, as many of us believe, natural sunlight, can rarely be matched in the home aquarium. Ye old fish guys of yore used to purposely raise their show fish for fall competition outdoors in the summer for this very reason. It has worked for me on several occasions as a few trophies and plaques can attest. All with less work than my fishroom buddies endure.

Tropical fish are ideal for the summer water garden, and better suited in many ways than the stalwart goldfish, koi, and “damnbusia” mosquito fish. To wit:

• their small size makes them perfect for a variety of sized water features
• no need for aeration or mechanical filtration for small to medium species.
• little if any feeding is required
• much smaller biomass results in less algae and water fouling
• will not eat nor destroy our precious plants
• greater variety of shapes, colors, finnage, and behavior
• developing your own strain of fish

Before embarking on tropical fish in your water garden, I want to share with you how I, a hardcore aquarium hobbyist turned water gardener, have been doing this over the past 10 years with lessons learned the hard way ...

Since I use tub ponds, this makes retrieving fish easier, especially when I tear down in autumn. Surplus fish that I cannot house inside are disposed of in a variety of ways: (1) monthly fish club auction; (2) local pet shop; (3) given away to responsible fish keepers, and (4) sold off on www.aquabid.com in the case of much-desired species.

A common misconception of using tropical fish in your water gardens is that they will get sick when the temperature drops or that they cannot tolerate anything else than “tropical” water temperatures. In my 10 years “summer tubbin” I have never had a tropical fish contract Ich ((Ichthyophthirius multifiliis, white spot disease) or get sick from nightly or end-of-season temperature drops. The Ich parasite develops in the gravel bed of aquariums, which are a moot feature of my portable ponds.

The mistake people make when using tropical fish in water gardens is that they put them out too early. Some tropical fish that have been accustomed to pet shop temps in the mid 70’s-80’s F (21+-27+ C) may become stressed when placed in water below 70 F (21 C) degrees. However, once they are accustomed, they handle temporary drops (overnight or day) to 60’s or even 50 degree F (15+ or 10 C) water temperatures with no problem (remember: water temperatures are warmer than air temperatures at night). It is the extended or sudden temperature drops (like with a water change or cold snap) that might cause problems. However, many of the Central American livebearers and mountain Asian barb species prosper well into the fall when daytime water temperatures are in the 50’s F (10+ C).

Those of you in the southern US zones will naturally have a longer tropical fish and plant season than we do here in the north. Regardless of where you live, my rule of thumb (learned the hard way) is to put out your tropical fish when you put out your tropical waterlilies (>70 degrees F [>21 C] water temperatures). For me in Zone 6, that is usually Memorial Day weekend or soon thereafter. Just watch your Weather Channel and make sure the week ahead does not get colder. If the forecast predicts cooler temps -- wait! (I know . . . this is difficult.)

I take in my regular tropical fish in September, but let my cool-water species stay out through October. Again, watch the weather forecasts and get them in before a long cold snap or freeze comes. I lost several species a few years back in outdoor aquariums when a multi-day frost came in mid-September (tubbed fish did much better). You lucky ones in the southern zones can enjoy another month or two.

Your next consideration is where to use tropical fish in your water garden. My water gardening is strictly “summer tubbin.” I employ a variety of receptacles ranging in size from 5 to 70 gallons (19 to 265 liters) around my property. Tropical fish are perfect for small water features, and will breed and school in larger tubs (or ponds). This makes end-of-season retrieval easier for me than those using large ponds.

At its simplest, the big box store 20 gallon (76 liter) round plastic utility tubs sold for under $10 make for a great tub pond. They come in a variety of seasonal colors to match to your outdoor décor. If well planted, there are several species that will flock breed in these, especially livebearers. These containers have pluses and minus, however. They are deep enough to hold in heat and provide cool zones for your fish. But their taper towards the bottom makes it challenging fit a variety of plants. They will also crack after about 10 years, or sooner if not stored away from winter winds.

Better for about $20 are the pre-form barrel liner tubs, which are also 20 gallons (76 liters) but have a wider bottom and are more pliable. Either container can overheat, however, when placed on concrete in full sun. This heat is great for breeding labyrinth fish, but I have found it also leads to more stagnant conditions. This effect is mitigated by placing the tubs on your deck, or on slats where air circulation can occur.

Next up are the pre-formed ponds which are sadly not as readily available in hardware and garden stores any longer. I use several of the $35 34 gallon (129 liter) shallow round tubs, as they contain 3 shelves for my marginal aquatics collection. This flexible design along with their 36 inch (91 cm) diameter makes for good flock breeding while creating a diverse plant arrangement. However, they are also raccoon friendly! (More on this in another installment.) As you know, there are many other sizes and shapes of pre-forms that can be dug in or left free-standing.

Another option for me, which are especially helpful for larger waterlilies, are the Rubbermaid structural foam stock tanks which can be special ordered at your hardware store or purchased at farm supply outlets. These are the only tub ponds I keep out all winter without fear of cracking. At about $70 for a 70 gallon (265 liter) (40”L x 32”W x 24”H [102x81x61 cm]), they are an investment that will last a lifetime. No shelves (more next time on how I solve that problem) but great temperature control under any setting and a handy drain at the bottom. There are smaller and larger sizes available. See the Rubbermaid Commercial website for details.

Of course, because of the small size of most tropical fish, any container can work. I may utilize 5 gallon (19 liter) buckets for raising fry or small fishes if there is some shade, as well as large plastic containers if they are buttressed so as to avoid bowing or cracking. Three gallon (11 liter) decorative flower pots worked beautifully for guppies and micro-potted marginals last year. Under my deck, I often setup an outdoor fishroom like our Hawaiian aquarium hobbyists enjoy. If you go this route, keep in mind that fish are more susceptible to freezing in such tanks, and unless shaded, algae will cover the glass.   

< A variety of containers

Outdoor
fishroom >

What about filtration and aeration? Unless you plan on keeping the larger tropical cichlids, catfish or barbs, I eschew mechanical filtration and use nature’s vegetative bounty for removing all the nitrogenous wastes these little fish create. Oxygen is not a problem when lightly stocked, or if the pond/tub is wide, thus providing ample surface area for gas exchange. On a side note, why you pond folks still speak of “oxygenators” makes us aquarium hobbyists chuckle. Surface area is the primary determinant of oxygen content. Not amount of plants will overcome a small surface area!

So Which Fish?

Theoretically, any of the thousands of aquarium-friendly freshwater tropical fish can be used in the summer water garden (or spring to fall for you in the deep south). The species I will be reviewing are the ones I find most hardy, small in size (1”-3” [2.5-7.5 cm]), available at retail (or via Aquabid), do not hide from their owners, and are relatively easy to breed.

Temperatures listed are minimum maintenance water temps to assist you with timing their removal from your pond as the season winds down. Water temps in the 90’s F (32+ C) during the day are generally tolerated. A temporary cold day that warms up again should also not effect them. As recommended above, the real issue is acclimation from a warm retail store to the varying temps outdoors. Put out your tropical fish when you put out your tropical waterlilies (>70 F/21 C)! 

Barbs-Danios-Minnows

Barbs, goldfish and koi fall in the same family of fishes (Cyprinidae), and share many of same features (barbels, shoaling behavior, fast swimmers). But the aquarium barbs are generally much smaller. Some barbs can be fin nippers, and many are good at eating thread algae. Their oxygen needs are somewhat higher than other aquarium fishes, so a couple of pairs for a 24” (61 cm) diameter barrel pond would be maximum for the below species. These species will tolerate and breed in a wide hardness and pH range, but neutral or slightly acid/softer water is their native chemistry. Females are usually more plump and less colorful than males.

• Rosy Barb (Puntius conchonius). Hails from southeast Asia. Males are more colorful, so obtaining a pair is relatively easy. Flock breeds for me in 36” (91 cm) tub ponds. Very active. Minimum maintenance temp 16C/60F.

• Odessa Barb (Puntius padamya). Another Asian beauty with beautiful red body band and yellow dorsal. Flock breeds for me in 36” (91 cm) tub ponds. Minimum maintenance temp 16C/60F.

• Gold Barb (Puntius semifasciolatus). This is the color morph of the green barb developed by Tom Shubert of Camden, New Jersey USA, circa 1950’s. The fry resemble mini versions of their parents. Flock breeds for me in 36” (91 cm) tub ponds. Minimum maintenance temp 16C/60F.

• White Cloud Mountain Minnow (Tanichthys albonubes). This “poor man’s neon” may now be extinct in its native China, but is farmed for the commercial trade. A cool water fish great for the small water feature or tub and will flock breed. Minimum maintenance temp 5C/40 F.

• Zebra & Leopard Danios (Danio rerio). These speedy surface swimming egg scatterers are spawn eaters, but are so easy to breed that removing the parents will almost guarantee a brood. Minimum maintenance temp 18C/65F. 

The Livebearers

My personal favorite class of fish; livebearing occurs across several families, but represent only 3% of bony fishes. This highly evolved reproductive adaptation (vivipary) ranges from fertilization of eggs within the female’s body cavity to birth in 30 days (Poecilidae -- guppies, platies, swordtails, variatus, mollies), to umbilical cord fed embryos (Goodeidae) which take 60 days to birth. Poecilidae males have a stick-like anal fin called a gonopodium, and females can store sperm for monthly self-insemination for up to seven months.

Livebearer fry are born larger than egg layers/scatterers and thus, have a better chance of surviving hungry parents. All the fish below hail from Central America. In order to keep the females from being harassed, try to keep an even sex ratio, or better still, outnumber with females.

• Platy (Xiphophorus hybrid). Gold and blue varieties are the most hardy. A rainbow of color forms are available. Great for a small tub or water feature. Minimum maintenance temp 18C/65F.

• Variatus (Xiphophorus variatus or hybrid). Longer bodied than platies, the blue or yellow variatus are nearer to the true species and can withstand low temps for extended periods and cold snaps. Minimum maintenance temp 16C/60F. 

• Swordtail (Xiphophorus hybrid). These fish are
jumpers and get longer-bodied (up to 5 inches [13 cm])
so a tub of at least 36” (91 cm) is recommended.
Males spar with each other. Minimum maintenance temp 20C/68F. 

• Guppy (Lebistes reticulatus). Ideal for the smallest of water features, they are more likely to be seen in a water garden than the above Xiphophorus as they are primarily top swimmers/feeders. Fancy strains make a nice display with their large colorful tails. Hailing from South America, guppies are not as cold tolerant as their Central American cousins, contrary to popular belief. Minimum maintenance temp 20C/68F. 

• Ilyodon xantusi/furcidens. This lively goodeid reaches 4” (10 cm) and requires at least 30” (76 cm) width of surface area. Goodeids have evolved to rapidly changing temperatures and day-night and seasonal swings in their Mexican highland habitats, so they are some of the best tropical fish for a water garden with extended cold snaps. Minimum maintenance temp 18C/64F. Another goodeid with the same maintenance requirements is Ameca splendens (pictured). They are hardier but less lively. 

The Labyrinth Fish

Labyrinth fish are an ideal fish for small and shallow water gardens in summer, since they do not take in oxygen from the water. Rather they go to the surface for atmospheric air utilizing a lung-like organ in their heads. This makes them easily noticed in the water garden as they regularly come up to say "hello". Many are tough charges too, enduring fouled water that would weaken other fish. Males form a bubblenest for deposited eggs and guard the nest.

• Siamese Fighting Fish (Betta splendens). Unfairly kept in small vessels, your betta will do much better and be happier in your water garden. Only keep one male. Minimum maintenance temp 21C/70F.

• Paradise Fish (Macropodus opercularis). A cool water tropical ideally suited for the water garden and used by some lily growers year-round for mosquito control. Will flock breed readily in a 20 gallon (76 liter) tub. The orangey albino strain is nearly blind, and can be picked up in a cupped hand of water. Minimum maintenance temp 10C/50F.

• Blue/Gold/3-Spot Gourami (Trichogaster trichopterus). Can reach over 5 inches (19 cm) in length, but aquarium specimens are smaller. For breeding, adult size is required. Minimum maintenance temp 22C/71F.  

Be warned: moving your plants around you will probably hear yourself at the end of season as you tear down saying “now how did this fish get over here?”

Some egg layers devour their eggs, and thus require separating the parents from their eggs after spawning. I employ the “two tub method” here, where I will condition males and females separately for a week or two with live and frozen foods like mosquito larvae, blackworms, and baby brine shrimp. In the evening, when dark, I will introduce the flock into one of the tubs. They should spawn in the morning. I then remove them at dusk to the other tub (if I want to ensure a spawn I will remove these pairs as well after 24 hours to a different holding facility).

Fry should hatch in summer in about 24 hours, but will be too small to see. Commericial liquid fry food, green water, and/or frozen rotifers are good first foods to supplement their natural water garden diet. After a week you should be able to tell with a fine mesh dip net (e.g. brine shrimp net) whether your efforts were successful. Now you can start offering small foods like live or frozen baby brine shrimp, daphnia, and powdered flake food.

I hope this introduction to tropical fish in the water garden inspires my fellow members to take the plunge. Who knows? You may find yourself building a fishroom or rack when the season is over as you develop yet another hobby. Warn the wife.