Top 10 Ways to Solve Dirty Saltwater Aquarium Sand
1) Shallow sand beds can be cleaned with livestock
With shallow sand beds, less than 3" deep, your clean-up crew and utilitarian fish really help keep things clean as long as you stock the right animals. Some animals just pick the algae and leftovers from the top of the sand like hermit crabs and tangs, while others will burrow, sift, and turnover the entire sand bed filtering out detritus and waste along the way.
- Sand Sifting Gobies - Diamond Goby, Watchmen Gobies, Court Jester (Rainford's) Goby
- Nassarius Snails - Burrow into the sand and stir things up, eating detritus and leftover food.
- Omnivorous Snails - Eat detritus and algae growing on top of the sand.
- Tangs & Blennies - Herbivorous fish, in general, won't discriminate against algae growing on the sand in many cases.
- Hermit Crabs - Pick up waste and decaying matter setting on top of the sand.
- Sand Sifting Starfish - Best for larger tanks with a healthy sand bed to supply plenty of food.
- Sea Cucumber - Tiger Tail and Black Sea Cucumbers do a great job but should be reserved for larger tanks.
- Copepods and amphipods - Sift through the sand bed eating detritus.
2) If not livestock, use a siphon
Use a gravel vacuum to siphon and clean your sand bed with every water change. This will remove detritus and leftover food as well as turn the sand over, burying algae and other photosynthetic organisms. Just remember, if your sand bed is super clean you will have a hard time feeding any kind of animals that rely on the sand bed for food. Stay away from sand-sifting animals if you plan to regularly clean and siphon your sand bed.
3) Algae, cyanobacteria, diatoms, and dinoflagellates are all photosynthetic organisms
Many of the nasty sand-infecting organisms need light to grow and if you turn down your lights they will grow slower. Sometimes all it takes is less light in the tank which will slow down the growth of pests, then other more desirable organisms and creatures in the tank can effectively out-compete those ugly pests.
4) New tank, brown dust? Just leave it alone
Sometimes the best solution is no solution at all! Diatoms are pretty common with new tanks and show up as brown dust on the sand and other surfaces in the tank. They will generally go away on their own, no action is needed other than a little patience and regular maintenance.
5) Green algae = not turning the sand over enough
If you're getting green algae on the sand, your simply not turning it over enough. Green algae are photosynthetic and need light to grow and take time to grow. If you turn the sand over regularly, any algae that grow will become buried and be starved of light. Nassarius snails and Sand-sifting gobies can really help in this case or just physically stir the sand over on a weekly basis with a siphon.
You can also crank up the flow and run periodical surges to create a little sand storm and bury the unsightly algae. This works great with controllable powerheads that can be scheduled; just program a daily surge where the pumps run at full power for a few minutes just be careful not to kick sand up into the filtration.
6) Prevent detritus build up with plenty of flow
If detritus (fish poo/decaying matter) and leftover food is your problem, physically siphon the sand to clean it up and be sure you have ample water flow at all times helping to keep leftover food and waste suspended for easier removal via your filtration.
7) Purple or red colored slime is probably cyanobacteria
"Cyano" or cyanobacteria is pretty common in our hobby and contrary to popular belief, it's actually pretty easy to overcome. Just remember it takes some persistence and will take some time to resolve. You won't solve the problem overnight, usually it will take 2-4 weeks.
Read Article: How To Prevent & Remove Cyanobacteria
Physical removal with plenty of water flow is your first step in overcoming Cyanobacteria. If that doesn't cut it, consider using a competitive bacteria solution like Korallen-Zucht CyanoClean or Dr. Tim's Method. These work great but will take some time for the bacteria to populate and out-compete the cyano. These methods are safe, effective, and are generally a more long-term solution.
Finally, you have the popular anti-bacterial or chemical treatments like Chemi-Clean or Red Cyano Rx. These treatments are super effective at killing the cyano that is growing in your tank but won't prevent it from growing back. So you can rid your tank of cyano with a single treatment but don't be surprised if it comes back shortly after. The best approach here is to keep up with physical removal and after 2-3 treatments you should be able to get rid of it for good.
8) If it's not Cyano, it's probably dinoflagellates
Dinoflagellates are a bit different than cyanobacteria and can be are harder to get rid of. Dinos and cyano can look similar but instead of slimy red/purple sheets like you get with cyano, dinos show up as gold/brown stringy slime; snot-like is the best description. There are often air bubbles caught up in the slime as well. It can be confusing to the untrained eye but once you see both, you can tell them apart fairly easily.
There are also multiple types of dinoflagellates, all of which have a similar appearance but can require different solutions. So if you are battling with some ugly slimy stuff on the sand and rocks and cyano treatments just are not working, you might be dealing with dinos.
UV sterilizers are a great solution for some types of dinoflagellates and can also help reduce other disease-causing pathogens and slow down the spread of algae. If you think you are dealing with dinos, consider a UV sterilizer first for your tank but also begin to research dinoflagellates. These guys are pesky and hobbyists are effectively battling dinos with a number of different solutions.
9) Still got dinos? Consider a blackout, bacteria, and nutrients
Some dinoflagellates are photosynthetic. If you notice the dinos go away at night, then grow back each day when your lights turn on, they are photosynthetic dinos. Yes, they grow back every single day, that is how fast these things grow. If a UV sterilizer isn't working, try turning off your lights and blacking out the tank completely for 3-7 days. You will need to turn off the lights and cover all the glass panels completely to block out ambient light.
In combination with a blackout, consider adding a competing bacteria to help out-compete the dinoflagellates for resources in the tank. Brightwell Aquatics MicroBacter 7 and Dr. Tim's Dino Treatment Bundle are both popular bacteria choices for dinoflagellate treatment. While the hobby has yet to completely figure out the perfect bacteria dose to fight off dinoflagellates, this combination has worked for a large number of hobbyists in the fight against dinos. Its safe, easy, and worth your efforts in 99% of the cases.
Finally, you want to be sure your not running with 0 nitrate and 0 phosphates in the tank. If you find your tank is starved of nitrate and phosphate, dosing something like Brightwell NeoNitro or NeoPhos to increase nitrate and phosphate levels to a healthy balance has been known to out-compete dinos. These nutrients will directly promote the growth of healthy bacteria and other organisms that will then out-compete the dinoflagellates in your tank.
10) If dinoflagellates just won't go away, drop the DinoX hammer
If nothing works after 6 months or more of battling dinos, you can consider the chemical treatment DinoX. This is an algaecide that will kill many of the common dinoflagellates strains found in saltwater aquariums. Before dosing DinoX, consider the fact that it is an algaecide that could have negative effects on your coral. While its not definitively going to kill all your coral, it could have adverse effects and should only be considered as a last resort.