By Emily C on Tuesday, January 6, 2015 at 11:14pm
Proper substrate is one of the most important things you can provide for your hermit crabs and since people have many questions about it all the time, we wanted a go-to file that can provide answers and confirm theories.
Importance of Substrate A good substrate mixture must be able to break down organic matter such as feces, leftover exoskeleton, and uneaten food. It must be able to maintain a variable degree of moisture, without clumping, turning to mud, or drying out, and it cannot contain noxious or toxic materials, either man-made or natural. It must remain aerated (have air flow), moist, nutrient rich, and must not only house, but maintain a healthy colony of beneficial bacteria. Expanding on moistened substrate, it is important to know that it should be moistened with tap water that has been treated with a water conditioner such as, Seachem Prime or CLEAN well water, that contains no chlorine, chloramines, or heavy metals. You want this to be FRESH water, and not their salt water mixture as the salt can burn them since you would be unable to control the salinity. It does not need to be so drenched that it is flooded or muddied, it needs to be just wet enough that you can "build a sandcastle" out of it. In other words, if you were to squeeze a fistfull, it would neither crumble apart or leak excess water, but instead it would hold it's shape with ease - like play dough. This is because crabs need to be able to dig into it and have it hold it's tunnels so they can molt without fear of a collapse. The good news is, proper substrate can last for years in an enclosure, so there is no need to change it like pet stores have undoubtedly recommended you do. Good substrate is a necessary requirement for healthy inhabitants, and we cannot express this fact enough. All too often poor substrate results in unhealthy captives, death, or at the least, constant reconstruction of the enclosure. Nobody wants that. It's expensive, stressful, and unnecessary. When you think about how much time hermit crabs spend actually surrounded completely by substrate, it makes sense that we would want to make sure it meets all these criteria so they can be healthy, safe, and happy. Proper substrate can even be nutritious for your crabs and it is not unusual (or harmful) to see them eating at it. It is also not unusual for you to experience high levels of humidity when you first lay your substrate down. This can carry on for a few months, and it is not harmful to the crabs. Most all substrates smell "earthy" when first laid down, but after a while, a bad mixture will develop a sour, rotten smell, indicating the need for replacement. This is a fairly common occurrence, and is an indication of poor substrate mixture. It may be too wet, with pockets of stagnant water where bacteria and fungi have built up (we often refer to this as flooding and bacterial blooms), or it may lack nitrifying bacteria required to break down organic matter. Some substrates settle after a while, becoming hard and packed, and drying out easily. A good mixture will smell fresh and earthy for years.
*A Note About Beneficial / Nitrifying Bacteria Beneficial bacteria is one of the most important elements of the substrate, as it maintains the nitrogen cycle by breaking down organic matter and waste, and helps fight and prevent the spread of harmful pathogens that may be brought into the tank inadvertently. Without a decent supply of nitrifying bacteria, organic matter will not break down, instead rotting at (and beneath) the surface and turning into toxic materials, and harmful pathogens may run rampant throughout the substrate. Beneficial/nitrifying bacteria are introduced into the substrate via materials collected outdoors from healthy environments--with crabitat substrate, the addition of decomposing leaf litter is the most effective and recommended method for starting colony of bacteria. We will expand on leaf litter below as one of our amendments of healthy substrate.
Substrate Components: We still recommend starting with approximately a 5:1 OR 5:2 mixture of general purpose or play sand and coconut coir (EE) as the “base” of the substrate. A good rule of thumb is 3/4 brick (5:1) of EE to 1 1/2 brick (5:2) of EE per every 50 lb bag of sand. General purpose sand has a coarser consistency than play sand which is actually an advantage for our substrate since it helps promote proper drainage and is less prone to becoming compacted. Many of us currently use play sand, and this doesn't mean it's “bad” and needs to be replaced or shouldn't ever be used in the future, but it's important to be aware of possible drawbacks. If you are just now setting up your substrate, you can go ahead and choose to opt for general purpose sand if you would like. General purpose sand and play sand, both contain silica. Silica is also in a lot of beach sand (along with quartz, which is also in these sands) where our hermit crabs are native. Silica is the best kind of substrate for hermit crabs, and pool filter sand is another option, although not the healthiest option, but would work in a bind for those who may not have access to general all purpose sand or play sand. You want to avoid Calcium Carbonate (Aragonite and Calcite), which is what all of the sands from the pet store contain. Aragonite and Calcite (Calcium sand, Desert sand, Reptile sand) both harden up when they are wet then dried, which can result of cementing your crab into his shell and resulting in his death. Among that, calcium and desert sand also consists of harmful dyes and do not hold tunnels properly. Aragonite and Calcite are slightly different calcium carbonates in the way that they are bonded together differently. Oolitic sand, which is a very fine aquarium sand, do also contain Aragonite and not a proper sand choice. Coconut fiber, also called coco-fiber or coconut coir, is made from ground coconut husk. It's typically sold in compressed blocks or “bricks” that expand into a fluffy material when soaked in water. They do also have bags of it, but the "bricks" are they same thing, and less expensive. When it comes to various substrate mixtures, it often serves as a "filler", and also aids in moisture retention. Coconut fiber is preferred over peat moss because it lasts much longer, is less acidic, and does not inhibit the growth of bacteria. Coconut fiber is also more environmentally friendly than peat moss because it is harvested from farms, whereas peat moss is taken from the wild.
Amendments: Now it's time to look at the various soil amendments that, when added to the sand and EE mixture, will introduce and sustain the colonies of beneficial bacteria, help prevent clumping and compaction, aid in aeration, promote proper drainage, and provide a substrate mixture that remains safe, effective, and healthy, for years.
Leaf Litter: Decomposing leaf litter from a non-polluted wooded area is an essential element in any healthy vivarium substrate. Natural leaf litter not only adds texture and nutrients to the mixture, but also introduces beneficial bacteria and fungi. In non-trafficked forests, fallen leaves pile up around the bases of the trees throughout the changing seasons. At the top of the leaf litter will be the most recent layer, which should consist of whole, newly fallen leaves, in an early stage of decomposition. The lower layers are more decomposed, with the very bottom layers turning dark brown or black, and taking on a crumbly, soil-like composition. Materials from the top layer, all the way to the bottom layer, where the leaf litter meets the ground, should be used in the substrate mixture. Simply put on a pair of gloves and fill up a bucket, as needed. Avoid cedar and pine trees, as well as other noxious species, such as eucalyptus, oleander, melaleuca, pepper, bottlebrush, and brugmansia (Searcey, 2001). Make sure the spot of collection is not chemically polluted, otherwise serious health issues can arise in the captive environment. Hardbearing trees such as elk, oak, alder, aspen, beech, poplar, apple, ash, holly, privet, and birch are good choices for substrate (Searcey, 2001). Leaf litter should also be on the surface of your substrate (along with bark) at all times, as it contains cellulose which is a vital nutrient for crabs in the wild, and in captivity. If you have pill bugs/isopods/rollie pollies, they also munch and hide behind the leaf litter and bark.
Orchid Bark: Bark is added to the substrate to increase drainage and aridity. Orchid bark is used as a substrate to grow orchids on, and consists of cubed or irregular shaped pieces of bark from various tree species, but often firs (Searcey, 2001). Xerimulch, by Kellogg Co., is a similar landscaping mulch. Fir bark can be purchased in other forms, and is a good choice because it does not contain toxins or noxious resins, phenols, or sap like pine and cedar do. You want to avoid redwood bark and eucalyptus, as well, because it contains bacteria-inhabiting properties.
Milled Sphagnum Moss: Sphagnum is a variety of mosses that grow in bogs. Most of us are familiar with it as the type of moss most commonly used for the moss pits in our crabitats. When mixed into substrate it helps to retain moisture. Milled sphagnum moss is just long-fiber moss that's been finely shredded so that it has a “fluffy” texture and appearance. Milled sphagnum moss helps retain moisture while helping to keep the soil aerated and fighting clumping and compaction. It is also nutritious for the crabs.
Worm Castings: Worm castings, or worm feces, has a peat-like texture and provides structure for tunnels, porosity, aeration, drainage, and enhanced microbial activity. It is an odorless material that provides an abundance of nitrogen, phosphorus, potassium, iron, and calcium, and magnesium. It is another added benefit for your substrate that also provides nutrition for the crabs. Additionally, if you are concerned about the alkaline pH of your sand, worm castings are highly basic and will help balance it out.
Crushed Oyster Shells: While we spoke of Silica, Aragonite, Calcite and Oolitic sand, crushed oyster shell IS Calcite (Calcium Carbonate). The difference in being able to use this in your substrate, as opposed to calcium sand, is they are shaped like tiny rocks that would be near impossible to make a crab stuck in his shell. Furthermore, they consist of un-dyed/un-treated calcium so if a crab is munching on them, it's actually very beneficial to their skeleton, especially when underground and healing from his recent molt. When you think of the wild, you know that the beach has silica, organic materials such as roots, barks, leaves, exoskeleton, feces, quartz, old food, other decomposed material and, you guessed it, crushed oyster shell and even crushed coral shell. It is perfectly acceptable to choose a blend that has both crushed oyster and crushed coral.
Substrate Depth
Substrate depth is just as important as substrate components. Substrate exists so your crabs can molt and grow and stay healthy, provides nutrition with the amendments and provides exercise and fun for crabs who enjoy digging. It is very important that there is plenty of room for you to be able to safely have molters and crabs who enjoy digging regularly that won't come in contact with each other while underground. Molters are very vulnerable when down. If not careful, and not given adequate space to molt privately away from other crabs, then they can be killed, shell jacked by a shell envious crab, or have their nutritious exoskeleton eaten by the disturber. Their exoskeleton contains essential nutrients needed for them to harden their new skeleton back up. This also goes hand in hand with not having too many crabs for your enclosure, because if you're over capacity, then there is a greater chance of your molter(s) being disrupted, especially by the species who are more prone to digging for fun.We tell people to add a minimum of 6 inches of substrate, or at least 3x your largest crab to provide adequate space, but if you can add even more, that's actually recommended. We recently changed this advice to be at HALF of your tank height. With a 10 gallon or a 20 long, this is still 6 inches, but in larger tanks you can have something more like 8-13 inches. Experienced crabbers feel that 6 inches is rather low and the minimum should instead be several inches higher, unless your enclosure cannot provide it, hence our recommendation for filling to half the tank. If you need more room for climbing, you may be able to add a topper. Toppers do not give you more molting space and allot for more crabs, but it does give your crabs more room in their home to exercise and explore, while still providing what they need in their substrate. For the best substrate depth, 9 inches to 13 inches would be the most ideal, of course, like we said, dependent on your tank size. This is because, as we have mentioned, your substrate is pretty much permanent, needing no changing out unless you have some sort of emergency like an ant/mite/flea infestation or a flood/bacterial bloom. It is also because over time, your substrate provides the aforementioned beneficial bacteria and becomes "homely" to the crabs, which essentially gives them comfort and stability. Even their poop doesn't need to be scooped as your substrate can handle that bacteria, and if you have a clean up crew such as isopods, you hardly have to worry about mold from old foods. Yet another reason extra height is good, is because over time your substrate starts to "settle" and you lose inches. You want to be sure that you don't have to add to it for as long as possible because it's disrupting for the crabs (and you!), and if you add extra in the beginning, you have the room for the substrate to settle and still have enough height to not have to add to it at a later time .. at least not for a long time.
An Important Note: Molting is essential to their well-being. In the wild, they have all the molt space they need. It is different in captivity. Something you should take note of, is where they go down is not necessarily where they end up staying. Sometimes they leave a sign that they have gone down, such as a hole or a mound of substrate, but sometimes you won't be able to tell at all and the substrate will appear untouched. It is important never to dig up a crab that has gone down for any reason, with the exception of certain emergency situations. If you have provided the necessary substrate, then you should know that they can make tunnels all throughout their substrate. This means you don't want to assume they are somewhere they are not (unless they have left you window for peeking), cover up any holes or pat down the substrate (which can contribute to collapsed tunnels and compaction), or move your decorations around without being cautious (for example, they tend to molt under their pools).We hope this information explains to you why proper substrate, both components and depth, is important for hermit crabs, as well as which amendments you can use to achieve the ideal substrate. For a final note, here is more information on ratio of substrate and how much of it to use.
Ratios and Other Amounts
For so long, we have been told "5:1 ratio for substrate" and we took that to mean 50 lb bag of sand:1/2 brick of EE (coconut coir). Many of us here thought that amount of EE was too low in comparison, so instead we recommended closer to 5:2. We wondered how those numbers came about and thanks to some help, we calculated out that the 5:1 ratio amount has been incorrect all this time. 5:1 actually is closer to 50 lb bag of sand:3/4 brick. Due to this new info, we are no longer recommending 1/2 brick for every 50 lb bag of sand, and will instead be saying 3/4 brick - 1 3/8 (5:1.5), or even 3/4 brick - 1 1/2 (5:2), depending on who you ask since EE amount is also a personal preference. Please note, this doesn't mean you have to change your substrate if you've done it with the other amount. You do not need to follow an exact recipe for substrate, but we know that a guide, or a starting place, helps. What matters is that you have more sand than EE, and that your amendments are equal to or lesser than the amount of EE. So it looks something like 5:1:1 being sand:EE:amendments. To put it in simpler terms, let's say you want 9 inches of substrate. That would mean 5 inches sand, 2 inches EE, 2 inches amendments OR 5 inches sand, 2.5 inches EE, 1.5 inches amendments.. Something along that theme. With the amendments (orchid bark, worm castings, milled sphagnum moss, crushed oyster shell, leaf litter) you want to add, we estimate, 3 16 oz (48 oz) cup fulls of each one for every 50 lb bag of sand and 3/4 brick EE. It's too hard to calculate these additions perfectly, but that should bring you close to 5:1:1. These can also just be eyeballed with no measuring needed, or put in by the handful.
So 5:1:1 reads as 50 lbs sand:3/4 brick EE:48 oz of each amendment (roughly).
You can use EE bags instead of bricks. A bag is about 8.8 liters, whereas a brick is closer to 7 liters. One brick of EE is the equivalent of 14 pounds (when wet). A true 5:1 ratio would be 50 lbs:10 lbs, which equates to 50 lbs sand: 3/4 brick EE (10.5 lbs). As you can see, it's a little over by 2.5 lbs, but this is okay! We debunked it being 1/2 brick because that would equate to 7 lbs, which means we would come up very short in the end (15 lbs).
14 lbs = 1 brick
10.5 lbs = 3/4 brick
7 lbs = 1/2 brick
3.5 lbs = 1/4 brick.
5:1 = 50 lbs sand: 3/4 brick EE (10.5 lbs)
5:2 = 50 lbs sand: 1 1/2 bricks EE (21 lbs)
5:3 = 50 lbs sand: 2 1/4 bricks EE (31.5 lbs)
5:4 = 50 lbs sand: 3 bricks EE (42 lbs)
5:5 (1:1) = 50 lbs sand 3 3/4 bricks (52.5 lbs)
To calculate how much sand you need, you should use the rule of thumb of one 50 lb bag of sand for every 10 gallons of your tank, and 3/4 brick of coconut coir. So, if you have a 75 gallon, you want about 7 bags of sand and 5 1/4 bricks of EE. This does not take in consideration false bottoms, but be aware that substrate settles.
When factoring in amendments, remember it does NOT go by weight, it just matters that you use the same cup for every amendment. For the chart, I used a standard plastic 16 oz cup.
1 bag of sand (50 lbs) = 3/4 brick (10.5 lbs) = 5-10 gallon tanks = (3) 16 oz cups/each amendment.
2 bags of sand (100 lbs) = 1 1/2 bricks (21 lbs) = 15-20 gallon tanks = (6) 16 oz cups/each amendment.
3 bags of sand (150 lbs) = 2 1/4 bricks (31.5 lbs) = 29-35 gallon tanks = (9) 16 oz cups/each amendment.
4 bags of sand (200 lbs) = 3 bricks (42 lbs) = 40-45 gallon tanks = (12) 16 oz cups/each amendment.
5 bags of sand (250 lbs) = 3 3/4 bricks (52.5 lbs) = 50-55 gallon tanks = (15) 16 oz cups/each amendment.
6 bags of sand (300 lbs) = 4 1/2 bricks (63 lbs) = 60-65 gallon tanks = (18) 16 oz cups/each amendment.
7 bags of sand (350 lbs) = 5 1/4 bricks (73.5 lbs) = 75 gallon tanks = (21) 16 oz cups/each amendment.
8 bags of sand (400 lbs) = 6 bricks (84 lbs) = 75-90 gallon tanks = (24) 16 oz cups of each amendment.
9 bags of sand (450 lbs) = 6 3/4 bricks (94.5 lbs) = 90 gallon tanks = (27) 16 oz cups/each amendment.
10 bags of sand (500 lbs) = 7 1/2 bricks (105 lbs) = 90-110 gallon tanks = (30) 16 oz cups/each amendment.
11 bags of sand (550 lbs) = 8 1/4 bricks (115.5 lbs) = 110 gallon tanks = (33) 16 oz cups/each amendment.
12 bags of sand (600 lbs) = 9 bricks (126 lbs) = 125 gallon tanks = (36) 16 oz cups/each amendment.
13 bags of sand (650 lbs) = 9 3/4 bricks (136.5 lbs) = 125-150 gallon tanks = (39) 16 oz cups/each amendment.
14 bags of sand (700 lbs) = 10 1/2 bricks (147 lbs) = 125-150 gallon tanks = (42) 16 oz cups/each amendment.
15 bags of sand (750 lbs) = 11 1/4 bricks (157.5 lbs) = 150 gallon tanks = (45) 16 oz cups/each amendment.
16 bags of sand (800 lbs) = 12 bricks (168 lbs) = 150 gallon tanks = (48) 16 oz cups/each amendment.
17 bags of sand (850 lbs) = 12 3/4 bricks (178.5 lbs) = 150-180 gallon tanks = (51) 16 oz cups/each amendment.
18 bags of sand (900 lbs) = 13 1/2 bricks (189 lbs) = 180 gallon tanks = (54) 16 oz cups/each amendment.
Written by: Emily C, Lauren Y
The following was written by Emily C on October 29, 2015 to help explain this a bit more:
All too often we get rightfully asked about substrate and what it should consist of, how deep it should be, and what it should be moistened with. Substrate can be a confusing aspect of crabbing, but also one of the easiest once you understand it. We also get asked about whether or not it's mandatory to add the amendments we list. The short answer is no, it's not mandatory, but it is definitely 100% encouraged.
First, some perspective. What type of sand? Every beach has different kinds - silica/quartz, calcium carbonate (aragonite/calcite). That already makes it confusing to know which type we should use in our tanks. This is where it becomes very important to note that we have to modify our care to make a safe home for them within an enclosure, while still mimicking where they come from. We can not copy "the wild" to the letter, because in an aquarium it wouldn't be appropriate. Calcium carbonate based sands have a tendency to harden once it's been wet then dried out. It has been so dangerous that it can actually cement a crab into its shell, eventually killing the crab. It simply isn't worth the risk. Silica based sand is different. It can dry out like any other sand, but it doesn't have that same hardening effect, it's more "dust-like". This is one of the main reasons we suggest going with a silica based sand, such as all purpose sand and play sand (like for children's sandbox) instead of calcium sand (marketed as "hermit crab sand"), aragonite sand (marketed as reptile/desert sand), or another form of calcium carbonate based sand such as the ocean sand for fish tanks (CaribSea Ocean Live Sand).
Visualize a beach. On a beach, the sands are always kept moist. The top may dry out due to the heat/sun, but underneath that top layer it is kept wet enough for you to be able to build a sandcastle at any given moment. They don't have to worry about the risk of substrate getting too dry from heaters, lack of misting, too low of humidity, etc. Not to mention the fact that calcium carbonate sand is very fine, something you don't want in an enclosed aquarium because it's important that your sub has proper aeration (air flow) and drainage (to prevent stagnant/trapped water which leads to toxic blooms). We instead opt for play sand and all purpose sand because it's more coarse and allows for that drainage and aeration.
Now that you understand which types of sands we recommend and why we don't use the other types, let's think about what is all in the sand on various beaches. This ties in on why we encourage the use of amendments. So here we go, what's in the sand? Sticks, bark, pieces of coconut, leaves, exoskeleton, broken shells (calcium carbonate), washed up sea life, rocks, food, seaweed, flowers, dead bugs, grass, moss, and more. Adding similar items to ours not only helps to mimic what their natural substrate is like, but it improves the health of our substrate. Our substrate needs beneficial bacteria which supports the nitrogen cycle in order to properly break down any organic material (feces, dragged off food..). Because of this, we recommend using coconut coir as one of our base components along with the play sand/all purpose sand. Coconut coir, also called EE for Eco Earth in this group even though other kinds are available and just as safe, is environmentally friendly, not too acidic, does not inhibit the growth of beneficial bacteria, helps break down organic matter, helps hold tunnels in the substrate and lasts a long time. Sand and coconut coir work together in harmony as they compliment each other. What one lacks, the other has and using only one instead of both would not be in the crabs best interest as both pose problems on their own, problems that do not as easily exist when you combine them. For example, EE is more likely to become flooded, whereas sand is more likely to form a toxic bloom.
Now, each amendment (moss, leaf litter, crushed oyster shell, worm castings, bark) all perform a role in the substrate, as well as provide nutrients, support drainage, encourage substrate bacterial breakdown, and closely mirrors natural beach sand. This is all outlined in the file I linked in the beginning of this thread that you can read for more information. A special note is the crushed oyster shell - it provides the calcium carbonate or substrate is missing in a much safer and beneficial way.
So why can't you take beach sand straight from a beach? Many reasons! So many contaminates such as urine, condoms, cigarettes, oil, dirty diapers, dog feces, and more. On most beaches, it is illegal to take beach sand, especially as much as our tanks need. Beach sand may also be safe on a beach, but in our aquarium, it can be too fine and become compacted, or not have the proper drainage, or might not be silica based. Play sand is only a few dollars, and it's neither dirty, illegal, or the wrong type of sand.
As a final note to this information, I wanted to say to remember to moisten your substrate with treated fresh water, not salt. You can use tap water and Seachem Prime. The depth of your substrate should be at least half the tank, no matter your tank size.