Black Diamond Blasting Sand (BDBS) is a great budget black sand for aquariums. It comes with many benefits, as shown in "The Best Budget Black Aquarium Substrate: Black Diamond Blasting Sand." Unfortunately, there are a few downsides to using BDBS. But, with the cons that I list down below, I will outline a workaround if possible.
1. Diligent rinsing of BDBS is essential
Despite being an inert substrate, there is a lot of dust and oil residue characteristic of this substrate. Both of these are completely harmless for the fish, but they are aesthetically unappealing. To ensure you do not have cloudy water or an oily surface, make sure you rinse this substrate prior to using it, and rinse it well.
2. BDBS alone cannot sustain planted tanks
If you decide to use BDBS in a planted tank, the substrate must be supplemented with fertilizer and/or root tabs. Since the substrate has no cation exchange capacity, it offers no nutrients to plants, so fertilizers are necessary to provide for the growth of your plants. On the bright side, it is very much so possible for you to have a planted tank using this substrate, if you dose correctly.
3. The accessibility of BDBS is largely dependent on location
BDBS is only cheap if you can physically drive to a Tractor Supply Company store. So, if you do not live near one or if you live outside of the United States, BDBS no longer becomes a viable option, unless you live near a different store that carries it. Also, purchasing BDBS online from Tractor Supply Company inflates the cost significantly, now that you have to add in shipping costs. Home depot carries a version of blasting sand, but it is nowhere near as affordable (reportedly ~5x the price).
4. BDBS is difficult to slope for high-inclined aquascapes
If your intended aquascape requires that you create steep slopes out of the substrate, BDBS may not be the substrate for you. BDBS has a tendency to slide down easily, making steep slopes a difficult task. One potential solution is try to creatively anchor down the BDBS with hardscape or to use a base layer of different substrate under it.
5. BDBS carries a minor risk of anaerobic pocket build up
Unlike in gravel-like substrates, any substrates that can easily compact (i.e. sands) are prone to creating anaerobic pockets. These pockets come from the gaseous build up of byproducts from bacteria living on the substrate. BDBS is no exception to this risk. However, reports of this actually happening are very scarce, especially if you avoid the finer grits (i.e. 40-80). If you are concerned of anaerobic pockets when using BDBS, consider adding trumpet snails that will turn over the substrate. Note, BDBS is snail safe.
6. The are rare reports of BDBS containing bits of metal and mini-glass rods
These reports have been very rare, but if you are concerned about the metal, consider running a magnet through your BDBS while you are rinsing it. Regarding the mini-glass rods, these should be relatively harmless if they make it into your tank, and they will be very few and far in-between. Again, be diligent in your rinsing.
7. BDBS is not completely black
Upon close examination of the substrate, unfortunately there are these rust-like granules sprinkled about. While this may be an eye sore for some, I personally do not think it takes away much from the goal aesthetic of the black sand.
8. BDBS is difficult to gravel vacuum
This con is not specific to BDBS, but moreso applies to any sand. If you use the recommended 20-40 medium grit version of BDBS, you should not have any problems. The best practice of gravel vacuuming BDBS involves approaching the substrate with the siphon at an angle. It is also important that you hold the attached tube and kink it between suctions, so that the detritus gets suctioned up the siphon while the BDBS granules fall back down to the bottom.
Despite the cons, there is no question that BDBS still reigns supreme as the best budget-friendly black sand, for all types of tanks, with various types of livestock. BDBS may not be perfect, but you can achieve near-perfection with the aforementioned suggestions.