dsb smell

[jc]

I have only had my fuge set up for a few months and it was working great until recently. I am noticing a sulfur smell coming from the fuge. It is a 20g with 5" of sugar size sand and a ball of cheato floating around. The fuge does have lots of slimy algae in it which I think is from the light that the cheato grows so well with. I also hang my protein skimmer on the fuge. I read that it is probably sulfides but I have read conflicting ways of treating the problem. Is the flow supposed to be slow or fast? Should I add sand sifting critters or do I leave it alone?

[GaryP]

Bacteria in the DSB are breaking down proteins and producing the odor you are noting. Its probably a combination of sulfides and an organic chemical called mercaptans. Mercaptans are what they add to fuel gases (natural gas, butane, propane) to give them a detectable odor. These are both natural products of bacterial protein decay. The bacteria are just doing what they are supposed to do. I don't know there is any cure for it besides not feeding your tank. I've smelled that in DSBs that I have broken down, but never in a tank that was running. However, these compounds can be detected by the human nose at very low levels. That's why they use them for odorizing gases.

The flow in the fuge should be relatively slow, perhaps a couple hundred gph.

Light doesn't cause algae, nutrients do, especially phosphate. If the slimey algae is limited to the fuge, I wouldn't worry about it. If you are having problems in the display tank, I would suggest looking into some sort of phosphate scavenger.

I wouldn't necssarily add sand sifters. There probably isn't enough food to support them in the food, other then dead chaeto and that's not very digestible.

[jc]

Maybe I am feeding too much. I am using a mag5 so the flow is not too fast. I usually feed 1 frozen cube every other day. I don't like the smell maybe I could get rid of the sand and just use the cheato to reduce nitrates. I used both of them from day 1. Is cheato by itself enough to keep the nitrates low? Right now they are at zero.

[GaryP]

That doesn't sound like feeding to much to me, more like not enough to me. You're getting around 500 gph from that Mag 5. That's a lot for that size nano. You might want to go down to a maxijet.

You don't have a DSB in your tank? You are relying on the fuge for all denitrification? If so, that's probably not enough capacity for denitrification. There's only one way to find out.

[jc]

right, I dont have a dsb in the tank, it's in the fuge. the fuge is under the tank so the mag losses some power. Since i'm moving the tank I think I will skip the dsb and just run the fuge with cheato. could i add LR rubble to the fuge instead of sand? I want to keep the pod population high for my mandarin goby even though he eats frozen.

[GaryP]

I think I came up with a solution. I just needed to sleep on it.

I think the reason you are smelling the sulfides is that your water is low in iron. Normally, I think the majority of sulfides and mercaptans are precipitated as insoluble iron salts. I know the times I have broken my DSB's down I have seen a lot of it there. Once it has precipitated its basically inert and has no smell.

Iron supplements are available at LFS. They are usually used in planted tanks. It probably won't hurt your chaeto or coralline algae growth either.

Back to your question. I think without the DSB you are probably going to end up with nitrate problems. The guys I know that are running a BB are doing it with really large skimmers and a lot of labor devoted to siphoning as well as a lot of current to keep detritus from building up. I'll let you talk to the BB guys about what you need to do to run a pure BB without a DSB fuge. I'n not sure about the pods. They should do OK if you replace the DSB with rubble, although I was always under the impression pods laid their eggs in sand. Again, I'll let you talk to the BB guys about that. Texas Todd, would be a good person to PM about it. He's done a lot of research on running BB.

[jc]

Here is my plan. I will try the iron for a while and see if the smell gets weaker or stronger. If stronger then I will try to do just the cheato with LR rubble and a 1" bed of sand for the pods. If nitrates go up to high I will just restart the dsb with some fresh sand and try some additives from the start. Thanks for the info. It really is helping me out.

[GaryP]

Sounds good. Here is something like what I am talking about.

http://www.kentmarine.com/saltwater/ir.html