SUBSTRATE – This is updated info , for anyone who revisits this website from time to time. For a large ongoing colony, it is IMPORTANT to start with an undergravel filter, in addition to a normal filter. I used to recommend that a SANDY layer works best, with larger gravel on top. However, after several months or more, I have found that the sandy layer combined with a undergravel filter, will pack the sand (or crushed Onyx, etc) so dense that it stops the water flow into the undergravel filter. And with a fine sand, not even a power head can pull water through the undergravel filter once it packs, which can take several months. I now recommend a layer of small-stone natural gravel, covered with a layer of larger garden stones. The larger rocks (on top of the sandy layer) acts as a hiding place for the newborns! Don’t use colored “aquarium gravel”! A note – the colored gravel found in pet stores is painted rocks. Crays will eat the paint off the gravel, which is not good for the crays or the gravel. Use natural large stones instead of aquarium gravel, on top of your base of natural gravel. Use the large “garden rocks” that run from size of a quarter to golf ball size, commonly found in bags at the Lowes hardware garden section. The larger stones create larger places for babies to burrow into – and escape from when they grow larger. You will find that without an undergravel filter, no outside filter can really keep up, as these animals are messy. THIS IS WHY THEY ARE GREAT IN AQUAPONICS GARDENING SYSTEMS!
I have experimented recently with white marble rocks, with “river stones” or rounded rocks, and with lava rock, all commonly found in garden centers. Out of these, I find that the lava rock is most desirable. The other rock types have a lot of powder that must be rinsed out before adding to a tank, or it never goes away. The lava rocks are also light enough where the crays love to dig under them, the babies hide well in and under them, and water flows freely around them in the undergravel filter situation. I found that in my tanks with fine sand that was totally packed so the filter could not move water, I replace the fine sand in one spot with a mound of lava rock, and regain movement to the undergravel filter. Lava rock also contains a lot of healthy nutrients for plants, which is why it is used a lot with hydroponic growing. I recommend LAVA ROCK now over all other substrate types.
But, if you already use the fine-sand substrate which I previously recommended (as some of my own tanks do), I find that when your underground filter power-head can no longer move any water, there is a solution. If possible, move your crays to a temporary location for a couple of hours – even a ice chest with an airstone. Then, in the aquarium, go down to the impacted substrate, which you will find feel layered as hard as a rock, and dig. Using a fork and fingers, loosen the hard substrate until it is again porous and loose. Run your underground and external filters while you do so. Once the whole tank substrate has been stirred, give it an hour or more to settle. Siphon off the loose layer of gunk collecting on the bottom, the water will clear quickly. If you have plants outdoors (or indoors) you will find this dirty fish water & tank gunk will really help your plants grow and be healthy! And your UG filter power head will once again move water, after it coughs up some loose substrate.
The statements provided in this website reflect the personal experience of the owner, not the results of academic research per se.