Can You Run UV When Carbon Dosing?

If you've been considering carbon dosing but are concerned about whether your UV sterilizer will kill the entire operation, then you're certainly not alone. It's one of the most frequently asked questions, and I completely get why it seems so glaringly obvious. If you're carbon dosing to boost the bacteria in an attempt to better control nutrients, then shouldn't your UV just kill off all that effort?

Good news: Yes, you can use your UV sterilizer when carbon dosing, and I'm going to tell you why they are actually well-suited together.

What Does A UV Sterilizer Do?

First things first - let's debunk a popular myth. Your UV sterilizer isn't actually "killing" the bacteria like it's an underwater killing ray. What it's doing is sterilizing them by disrupting their DNA so they can no longer breed. It's actually more like putting bacteria in "time out" - they're still there, still busily decomposing nutrients, but they just can't breed anymore.

This works for us perfectly well because those bacteria will continue to graze on phosphates and nitrates even after going through your UV. They just won't be able to overgrow and create issues. 

What Happens When Running A UV Sterilizer And Carbon Dosing

This is where things get really interesting. Some researchers performed a close examination of this very same question using a 57-watt UV sterilizer (the same kind most of us already have on our tanks). They took bacterial counts days with the UV on and off, and voila. The bacterial counts remained essentially the same either way.

During a period of five days, they observed bacterial counts ranging from 60,000 to 90,000 per milliliter, as this is the natural fluctuation that occurs with or without your UV operating. They found that running a UV sterilizer did not affect the overall bacterial count, so don't stress about it ruining your carbon dosing scheme if you are running a UV sterilizer.

Carbon dosing doesn't do much of anything in your water column anyway. The magic is happening in all your live rock nooks and crannies, sand bed, and carbon media, where bacteria migrate in and develop those slimy biofilms we love to hate.

When you dose your vodka, vinegar, or whatever carbon source you're dosing, what you're doing is supplying fuel to these existing bacterial populations. They're hiding from your UV, munching happily away on carbon and turning your excess nitrates and phosphates into more bacteria. Nice, huh?

Your Protein Skimmer: The Real MVP

Talking about eliminating bacteria, your protein skimmer is doing much more of the hard work than your UV sterilizer when it comes to keeping bacteria at bay. If you have no clue about how protein skimmers operate, check out our in-depth article on "What is an Aquarium Protein Skimmer" - it's a game-saver for learning about your tank's filtration.

Your skimmer is continuously removing bacteria, dissolved organics, and all manner of gunk from your water by foam fractionation. The studies indicate tanks with effective protein skimming have bacterial counts of 70,000-140,000 per milliliter, whereas skimmerless tanks top out at 1.5-2.5 million! That is a massive difference.

As you're dosing with carbon, you'll want to wet out your skimmer somewhat so you can be confident that you are removing all the bacterial biomass that you're producing. That's where true nutrient export occurs.

Controlling Bacterial Populations In Aquariums

Now, here is something very critical that everybody discusses enough: having control of your bacterial populations when carbon dosing becomes a factor. You want enough bacteria to effectively degrade nutrients, but you don't want too many and have issues such as cyanobacteria blooms or bacterial film dominating your tank. Having trouble with cyanobacteria? Take a read of our guide on “Effective Methods for Eliminating Cyanobacteria.”

When you begin carbon dosing, you're oil to the bacterial fire. Without good export mechanisms in place (hello, protein skimmer!), those bacterial populations are going to go wild and give you all sorts of grief. This is where your UV sterilizer is your best friend.

By killing free-swimming bacteria in the water column, your UV prevents bacterial blooms from getting out of hand without letting your good biofilm bacteria get in the way. It's a safety net that has your bacterial populations under wraps without affecting the nutrient flow you desire.

The secret is balance. You desire good bacterial populations in your rock and substrate to process nutrients, but balanced populations in your water column so you don't have problems. Your skimmer accomplishes it by stopping runaway bacterial growth while your UV kills surplus biomass.

Running UV When Carbon Dosing Benefits Aquariums

Combining UV sterilizing with dosing carbon gives you some serious advantages:

1. Prevention of Disease: Since your good bacteria are comfortable in their biofilm homes, any nasty pathogens that are floating around are delivered the kill before they can cause damage to your corals and fish.

2. Crystal Clear Water: Ever wonder why some tanks simply seem to have that ideal clarity? UV prevents those pesky bacterial hazes from sneaking in and making your water seem "off," particularly when you're increasing carbon dosing.

3. Stable Parameters: By preventing free-floating bacterial populations from getting out of control, your UV prevents those pesky parameter swings from occurring when bacterial populations run amok.

4. Less Stress Overall: Your fish, corals, and other invertebrates are less stressed by waterborne uglies, so they can direct all their energy to developing and being pretty rather than to combating infection.

Things To Consider When Running UV When Carbon Dosing

Even though you can run a UV sterilizer alongside and carbon dosing, watch out for:

If your UV isn't bringing your nutrients down like it should, don't fault your UV. In the majority of cases, it's an issue of dosing quantity, skimmer adjustment, or bacterial populations simply requiring a little extra time to establish themselves.

The first few days after beginning carbon dosing, you'll experience some bacterial cloudiness that's completely expected. Your UV will do its best to keep it there, and in a few days, it should settle out once everything balances out.

Conclusion

Your carbon dosing takes care of the export of nutrients by nourishing good bacteria everywhere they need to be, and your UV maintains things clear of debris and stable by controlling water column bacteria. It is almost having the best of both worlds merge to provide the type of sparkling conditions that allow corals to grow like mad and make corals glow. 

Trust the process, keep an eye on your parameters, and enjoy seeing your reef flourish with this award-winning duo! If you would like to learn more about running your UV sterilizer alongside carbon dosing, or what carbon dosing methods we recommend for your aquarium setup, contact the Reefco Aquariums Team.