Previous posts in this 4-part series discussed the natural environment of cherry shrimp and their unorthodox method of feeding; or, more accurately, grazing. In this post, we’ll go over how to develop vibrant biofilm for your shrimp to graze upon.

I. The Basics: An overview of feeding aquarium shrimp

II. How Cherry Shrimp Eat: The biology and natural feeding behavior of neocaridina shrimp

III. The Edible Aquarium: Promoting biofilm in your shrimp tank (This article!)

IV. Feeding Cherry Shrimp: Primary foods and special treats (Coming soon)

The Importance of Biofilm in Shrimp Tanks

Unlike your average fish, cherry shrimp don’t gobble down food, but instead graze throughout the day (and night). Since shrimp hardly ever stop eating, they obviously need a steady supply of food. This is no problem in the wild: there is virtually always food available in a shrimp’s natural environment, wherever they land.

Our home aquariums may never reach the sheer variety and quantity of microbial life available in nature, but a well-established tank can do a fine job of keeping cherry shrimp well-fed and happy.

There is a caveat, however. Newly filled aquariums are sterile and lack the balanced ecosystem a shrimp colony depends upon—new tanks are a shrimp’s nightmare. The good news is that you can greatly speed up the maturation process.

NOTE: The following advice assumes you are keeping a natural tank, which is by far the easiest way to keep shrimp. That’s not to say you can’t succeed with a high-tech, super-clean setup, but that approach is both high-maintenance and requires a good deal of experience to manage.

“It surrounds us … binds us”

Biofilm is a much bigger subject than it would seem. Your first thought when you hear the word biofilm is probably a filmy layer of bacteria. Okay, well, yes … but it’s so much more! Those slime layers are actually full-blown biological systems of their own.

It may be invisible to us, but we are all entangled in a world of biofilm. Different kinds of biofilm flourish in ponds, the ocean … our teeth … and our aquariums. So really, you don’t need to do anything special to eventually grow biofilm in your tank: it naturally develops as a tank matures into a balanced ecosystem.

What is Biofilm?

Biofilm is a community of microscopic lifeforms that literally gel together and attach to surfaces, creating a kind of ‘microbial city.’ Biofilm is typically made of different kinds of bacteria and other organisms.

5 stages of biofilm development.
Stage 1, initial attachment; stage 2, irreversible attachment; stage 3, maturation I; stage 4, maturation II; stage 5, dispersion. By D. Davis, CC BY 2.5 via Wikimedia Commons

To create biofilm, certain microbes change their “free-floating” behavior to a more symbiotic form. These changeling bacteria stop floating and begin to organize themselves into a community, spreading a gooey web over physical surfaces such as rocks, plants, or the substrate. The organisms within this web matrix can function in various symbiotic ways: further matrix production, spore maturation and release, overall motility, and various other communal activities (many as yet unknown).

Biofilm also protects bacteria within the biofilm: they can share nutrients and enjoy the matrix’s protection from environmental hazards like toxins–including antibiotics–or drying out.

Fossilized Biofilm is a Thing

Microbialite that resembles underwater reef

Microbialite formations in Pavilion Lake (British Columbia) NASA Pavilion Lake research project, Public domain, via Wikimedia Commons

You’re probably not surprised to hear that biofilm evolved many millions of years ago. It was a big deal back then, too. Over time, layers of thick biofilm sometimes hardened into fossils!

Mature biofilm can grow to become visible to our own eyes. Fossilized biofilm sedimentation structures are called a “stromatolite“; these are the oldest fossils on earth. Microbialites are another bacteria-made fossilized phenomenon: they look like underwater reefs. As the biofilm assumes a physical shape and color, it may become quite beautiful … if you can see past the fact it is literally a tower of bacteria.

Biofilm in the Shrimp Aquarium

In other words, shrimp have been munching on biofilm for a long, long time. They love it. In our aquariums, biofilm allows shrimp to feed naturally and healthily. It tides them over between regular feedings and nourishes their tiny babies. It only makes sense to try to grow a rich inventory of biofilm for shrimp to graze on.

(There is some evidence cherry shrimp are actually feasting upon the web matrix instead of the animalcules within it. Maybe they’re just scooping up delicious bacterial frosting?)

Ten Tips for Growing Top-notch Biofilm

Biofilm grows naturally over time. If you have a stable aquarium well-stocked with plants that’s been running for several months or years, your tank will have grown at least some biofilm without special effort on your part. It’s really the biofilm of newer aquariums and those heavily stocked with dense colonies that could use extra attention.

The value of an older, mature tank was well known to aquarium old-timers. In the early decades of the hobby, “aged water” was considered almost magical … but simply being aged wasn’t the real reason for its value. The balanced microbial environment in the water of an older, well-established healthy aquarium supports higher lifeforms like fish and shrimp.

There are some things we can do to promote quicker growth. If you’re an experienced aquarist, you probably know many of these steps, but it’s still worthwhile to review the list.

1. Inoculation

This sounds more technical than it is. Essentially you add aged aquarium water, cycled mulm or–best of all–filter squeezings from an older, cycled aquarium. This is the single best trick for getting a new tank and its biofilm up and growing quickly. (Older tanks won’t benefit as much, assuming they have already cycled.)

Simply pour the older “dirty” material into the new water and stir it up. It’s great if it makes the water murky … the debris will settle down, but meantime the microbes will seed themselves all over the aquarium. This one action can almost instantly cycle your tank and make it habitable for shrimp.

2. Provide Attachment Sites

It’s important to provide your microbial population with physical attachment sites so they can retire from their free-swimming lifestyle and settle down to make biofilm. If the tank is completely bare, bacterial populations will attach to the glass, but the more attachment sites the better!

Substrate, rocks, and plants provide a myriad of crevices for bacteria to make their homes in. Keep this in mind when setting up or re-decorating your aquarium.

Sponge filters and other forms of biological filtration are basically attachment super-sites. They are effective because they offer many chambers in the foam for microbial colonization. The constant gentle flow of water keeps nutrients available to these waste-processing colonies.

In nature, it would take a large volume of water to contain enough microbes to remove an equivalent amount of waste. So, in effect, biofiltration increases the volume of water available in the aquarium.

3. Plants, Plants, Plants

A planted tank is the easiest and best way to keep your water and microbial populations healthy. Besides providing extra attachment sites, a growing plant removes metals, waste, and other potentially toxic substances from the water and helps oxygenate the water.

Probably any living aquatic plant is a positive addition to the tank, but faster growing species pull more toxins from the water. Shrimp colonies do very well with high-growth Riccia, Anacharis, and guppy grass … but they also love cleaning the broad leaves of slow-growing Anubias. Pick the plants you like best!

4. Light

Another basic element that produces shrimp-quality biofilm is sufficient light. It not only helps plants grow, but also the algae and assorted tiny things in your aquarium that we don’t even see.

Light is not particularly important to the shrimp, but it keeps the plants growing and the cycle of life moving in the tank–which IS important to them! Some plants require high light, some don’t mind a bit of shade, so do a little research and provide the right amount for your setup. Correct lighting = healthy plants = biofilm production and healthier shrimp overall.

5. Snails

Snails are great friends of shrimp and plants. Small pond snails, the common Ramshorn, Malaysian Trumpets or larger species like Nerites help keep algae down and reduce the chance of rotting food spoiling your tank. Snails even seem to help with biofilm; perhaps they leave a bit of slime behind that helps fertilize microbes. (This last thought is merely personal observation.)

Some hobbyists don’t like snails in their tanks, thinking them unsightly intruders. Snails are harmless to shrimp, but they can overpopulate if you feed too much. Actually, many snails may overpopulate if you are simply ensuring a good food supply for a breeding colony. With time, their population should eventually balance itself out.

If you decide to eliminate snails, it will be more time-consuming to keep your aquarium clear of plant debris and the glass clean. It is not impossible, of course, but be prepared to spend extra effort cleaning and monitoring.

6. Filtration

This was mentioned under #2 when advising on attachment sites … but filtration deserves attention on it’s own. The myriad attachment sites within filter foam promotes colonization by waste-consuming bacteria: this is the basis of biological filtration. You will notice your shrimp clinging to the foam and grazing once it’s well-colonized with fun-to-eat microbes.

Not to disparage the other two kinds of filtering, but mechanical or chemical methods are inferior for shrimp-keeping. Ammonia and nitrites caused by wastes are especially deadly to shrimp, and the microbes populating biological filters transform these toxins safely and naturally as part of their natural cycle. This is gentler and less prone to over- or under-filtration than trying to physically remove wastes from water or chemically neutralizing them.

The wonderful thing about biological filtration is that the microbes naturally adjust their populations in response to the quantity of ammonia and nitrites in the water. The microbes can multiply quickly to handle increasing waste loads (to a point, of course). Mechanical filters can clog or become overwhelmed with waste, and chemicals can be inexact in a changing ecosystem; biological filters automatically adjust their toxin-removing microbial colonies as the environment changes.

Sponge filters and other biological media can become blocked with debris and need to be cleaned occasionally. Be aware their precious bacterial cargo can easily be swept away or poisoned by chloromines and other disinfecting chemicals in treated tapwater. To avoid sterilizing your cycled media, the best practice is to simply squeeze the filter in a bucket of old aquarium water during a water change.

7. Supplementation

One popular supplement that has properties said to increase biofilm is Bacter AE. Other products make similar promises. Bacter AE comes in a powder that you sprinkle into the aquarium. The powder distributes itself all over the tank. It can help kickstart the ecosystem, and it has some claim to helping babies survive.

The powder is said to improve water quality and help develop healthy biofilm in your aquarium. The manufacturer touts Bacter AE as having important microorganisms along with amino acids and enzymes. It has even been suggested it’s made of powdered dry biofilm.

The popularity of Bacter AE with shrimp-keepers suggests it performs well for many users. It can be a nice addition to build biofilm … with one caveat: don’t oversupplement!

Bacter AE and any such products should be used with discretion: a tiny bit goes a long way! Ignore the label’s feeding recommendations, which will lead to the overburdening of the water with organics (in my own unfortunate experience). It can lead to fouling and shrimp death. Just add a tiny pinch to start with and monitor the results!

8. Add Catappa (Almond) Leaves

Another beneficial addition to consider for growing biofilm is Catappa or Almond leaves. These come from trees that originate in the same geographical areas as cherry shrimp: you can well imagine the leaves are continually dropping into streams and other water sources with cherry shrimp on hand to help them decompose.

The leaves are reputed to help stimulate biofilm and condition the water. At first the shrimp will largely ignore the leaves, but after a week or so the leaves start to taste delicious and you’ll notice shrimp camping out on their surface. Gradually your colony will skeletonize the leaves … be sure to refresh with another batch to season before it’s all gone!

One thing to know about Catappa leaves is that they carry tannins that can turn the water a golden brown. This is a good thing overall, as it’s healthy for shrimp (and many fish!); many aquarists come to like the color and seek it out.

It’s a good idea to boil the leaves for a minute or two for quick sterilization!

Tip: Longer boiling times remove more tannins from the leaves, so consider boiling a couple of extra minutes if you’d rather your aquarium water not have a brown hue.

9. Scatter Feeding

Another way to build biofilm and help ensure all the shrimp get something to eat is to crush their food into a powder and sprinkle it on the water. As with Bacter AE and other powdered probiotic additives, the small particles spread all over the tank. Be aware that this method feeds EVERYthing in your aquarium–snails, seed shrimp, detritus worms, etc, etc. Along the way, it also feeds the bacterial population and, theoretically, helps to grow biofilm.

This tip is explained in a video from Marks’s Shrimp Tanks (great channel!). It can increase colony size and baby survival. The video’s recommendation is to use goldfish flakes, perhaps for the protein profile. You might try crushing shrimp pellets or granules instead. It may be that powdered flakes promote better biofilm growth, so it is worthwhile to experiment using Mark’s recommendations.

DON’T OVERFEED! Scatter feeding infiltrates the entire aquarium with perishable food matter that can’t be cleaned without disrupting the whole setup. It’s important that the powdered food be eaten fairly quickly, before too many food particles disintegrate into the substrate or water column. For this reason, the scatter method probably shouldn’t be an everyday routine.

Your colony will need to be of a certain size before you can successfully scatter feed. Make sure there are enough critters available to consume the bits before they spoil!

10. Avoid Overcleaning

One final bit of advice: don’t overclean your tank. Constantly vacuuming the gravel, wiping off the glass, changing the water, scrubbing down hardscape, and replacing old bacterial-laden media with sterile new material can impede the development of biofilm. You don’t want your filter media to be TOO clean!

Be gentle with your microbes. A well-cycled tank keeps its own water clean and healthy, and sterilizing your system through over-cleaning can destroy the microbial balance.

REMEMBER: Processed tapwater often contains chloromine to kill bacteria, and it can wipe out your beneficial microbes too. The easiest way around this is to clean your filter and hardscape during a water change, using the aged water you’ve just removed.

Biofilm Unchained

This might beTooltip Text more than you expected to know about biofilm, but it’s an important part of shrimp-keeping! Biofilm helps provide the pastures upon which your beautiful little flock grazes.

Now that we’ve provided our colony with a full-time feeding station in the form of biofilm, the next and final post in this series will get into foods that provide regular feeding.