Vodka dosing issue...

[Joe w1994]

I have been trying to increase vodka dosing on my 800 gallon shark pond and everytime I try going over 13 m/l the water gets blurry. What can I do to avoid this. Running a sro 6000 ext and a regal 300 skimmer. Any help or ideas whats causing it would be appreciated. Dose all my other tanks and never have had this issue.

 

[EnterName]

You get bacteria blooms when you're adding too much carbon. By dosing alcohols into your system, you're providing bacteria with what was apparently a limiting resource (organic carbon), and once you lift that limitation, they spread through the entire water column faster than they end up in the skimmer. This can also cause excessive bacterial growth in your tank's plumbing or power heads, so be careful not to clog anything.

Carbon dosing can only do so much before it starts causing issues, so I can't recommend increasing the amount you're using if you're already experiencing bacteria blooms. These blooms consume a lot of oxygen, and sooner or later you might end up feeding bacteria that aren't beneficial.

If you're trying to reduce nutrients with carbon dosing, you may have hit the limit and will need to resort to other means, or at least distribute the dosing throughout the day in very small amounts with a dosing pump. I would however recommend phosphate adsorbers like granular ferric oxide (GFO) for phosphate issues and water changes for nitrate issues instead.

 

[Joe w1994]

You get bacteria blooms when you're adding too much carbon. By dosing alcohols into your system, you're providing bacteria with what was apparently a limiting resource (organic carbon), and once you lift that limitation, they spread through the entire water column faster than they end up in the skimmer. This can also cause excessive bacterial growth in your tank's plumbing or power heads, so be careful not to clog anything.

Carbon dosing can only do so much before it starts causing issues, so I can't recommend increasing the amount you're using if you're already experiencing bacteria blooms. These blooms consume a lot of oxygen, and sooner or later you might end up feeding bacteria that aren't beneficial.

If you're trying to reduce nutrients with carbon dosing, you may have hit the limit and will need to resort to other means, or at least distribute the dosing throughout the day in very small amounts with a dosing pump. I would however recommend phosphate adsorbers like granular ferric oxide (GFO) for phosphate issues and water changes for nitrate issues instead.

On a smaller system id agree on performing water changes but on a system this large I dont think it seems very feasible, considering i would probably be changing 300 gallons give or take a week or 2 to keep nitrates at a desired level.

 

[Privateye]

You could use a denitrification reactor instead. It's still possible to get some cloudiness if you're overdosing a lot (rare IME) but since the carbon would be introduced to the water going into the reactor, the bacteria in the reactor would get the first opportunity to consume it. That would leave less available in the water column of the tank for the planktonic bacteria to proliferate.

 

[Joe w1994]

You could use a denitrification reactor instead. It's still possible to get some cloudiness if you're overdosing a lot (rare IME) but since the carbon would be introduced to the water going into the reactor, the bacteria in the reactor would get the first opportunity to consume it. That would leave less available in the water column of the tank for the planktonic bacteria to proliferate.

Which would you reccomend for my system?

 

[EnterName]

On a smaller system id agree on performing water changes but on a system this large I dont think it seems very feasible, considering i would probably be changing 300 gallons give or take a week or 2 to keep nitrates at a desired level.

Fair point, I forgot about the size of the system, sorry about that.

I like Privateye's idea. Macro algae reactors, biomedia reactors, reverse flow deep sand beds, and other solutions might be able to help a bit. It depends on how much you can fit in your sump. You can also try to get a second or simply larger skimmer if possible. The more dirt you get out, the better.
The more tedious option would be to rinse rocks you can take out in a bucket with tank water to get rid of a lot of detritus that is just decaying and releasing nutrients. You could also start replacing the substrate in small batches, which is another detritus trap. Adding some dead dry rock in the sump if you have space left can also help by offering more surface area for beneficial bacteria. There are many small improvements, but nothing will immediately bring your nitrates down.

If your tank is running fine, you might also be able to simply ignore the nitrate readings. If you read through Randy's article on nutrient target ranges, you will see that many very good-looking tanks have very high nitrate levels and seem to run without any problems.

 

[Joe w1994]

Fair point, I forgot about the size of the system, sorry about that.

I like Privateye's idea. Macro algae reactors, biomedia reactors, reverse flow deep sand beds, and other solutions might be able to help a bit. It depends on how much you can fit in your sump. You can also try to get a second or simply larger skimmer if possible. The more dirt you get out, the better.
The more tedious option would be to rinse rocks you can take out in a bucket with tank water to get rid of a lot of detritus that is just decaying and releasing nutrients. You could also start replacing the substrate in small batches, which is another detritus trap. Adding some dead dry rock in the sump if you have space left can also help by offering more surface area for beneficial bacteria. There are many small improvements, but nothing will immediately bring your nitrates down.

If your tank is running fine, you might also be able to simply ignore the nitrate readings. If you read through Randy's article on nutrient target ranges, you will see that many very good-looking tanks have very high nitrate levels and seem to run without any problems.

No problem. Wouldn't mind trying different things to reduce nitrates just dont know how to size it up for this size system.. for normal fish I would agree and not think much of it, but i believe as I've read sharks are far more sensitive to high nitrates than other fish.

 

[Privateye]

Which would you reccomend for my system?

That's a good question. I have no experience with any of the options sold, so while I can show them to you I can't speak as to how well they work.

Here are some things I've seen:

Sulfur Denitrifier from BRS. The process is a bit different than denitrification with a carbon source. I've read some papers on it long ago but I've never used the sulfur method. It's more of a steady thing than something you dose often, which is a nice feature. I forget the other pros/cons though. This unit is rated for your tank volume. I see there are some other brands offering similar products too.

Bio-pellets are a cool concept, but I've also never used them. These are both a carbon source and a home for the denitrifying bacteria. They are meant to tumble slightly in the flow (you can buy reactors for them, or make your own for a system of your size). You replace them over time as they are consumed by bacteria.

I've mostly worked with DIY reactors on larger systems, with a carbon source. The carbon source (I've only used molasses and methanol, but vodka is better and safer respectively) is introduced with the water being pumped into the reactor, using a dosing pump (that can push the liquid in, despite the pressure from the water pump). The water flow needs to be low. In your case likely below 1 gpm. The carbon dose depends on your nitrate concentration and production. The effluent from the reactor flows back into your system, ideally where your biofilter is because the nitrite coming out of the reactor will be high. In the reactor you just have some biomedia (maybe 30-40% of the reactor volume if using K1 media).

The way the carbon method works is that the water flow into the reactor (or within a bio-pellet) is slow. This allows heterotrophic bacteria to colonize the first part of the bio media, and while they consume some of the carbon, they also deplete the oxygen. That leaves the rest of the media without oxygen but with some carbon, and then the denitrifying bacteria to do their work. They convert nitrate into nitrogen gas, which exits your system easily through off-gassing. The elevated nitrite is because nitrite is an intermediate step in the process. The other benefit of carbon-based reactors is they boosts your alkalinity, but not in an unsafe way - they restore 50% of the alkalinity lost through nitrification.

You just don't want your nitrates to get too low with such reactors because then they produce hydrogen sulfide instead. These are poweful management tools, but don't starve the bacteria of their food source! So you don't base your carbon (e.g. vodka) dose on a nitrate level, but instead based on changes in nitrate. When nitrate goes up for a little while, you increase your dose. After it falls for a little while, you decrease your dose. Your nitrate will go up and down as needed.

Like I said, I'm not well-versed in the sulfur method and I don't have time to read enough about it to compare right now, but I wanted to at least reply. Both methods will lower your nitrate - I just don't remember the byproducts and quirks of the sulfur one.