Skimmers and nitrates

[loganj]

This may sound kinda dumb. I have a couple of questions about skimmers and nitrates. First, all I have read about skimmer efficiency says that contact time is the most important thing. This is why larger, taller skimmers work better. Wouldn't it be better to use a smaller pump to slow water flow through the skimmer body? It seems like this would maximize contact time and be more efficient.
On the subject of nitrates, I know the LR will handle the conversion of ammonia/nitrite just fine and the DSB will take care of the nitrates. As long as there is a DSB in place, does it matter how the ammonia/nitrite is converted? What about a FO tank with very little rock and a couple of Emp 400's with bio wheels or a wet/dry? Would a DSB control the nitrates in this type of tank? I know the LR aids in nitrate control, but doesn't most of the anoxic bacteria live in the sandbed? The reason for the question is a friend of mine has a 135 with about 40-50lbs of rock. It is using a Oceanic wet/dry. It is stocked with a large wrasse,a moray, and a trigger. I think a volitans is on the wish list also. I wonder if a DSB would help with the nitrates in this tank? I know it won't handle all of it, but I'm looking to keep them down some between water changes. Nitrates are off the chart in this tank right now.
Logan J

[Hara]

Refugium....I can't say it enough. We had phosphates off the chart, no matter how many water changes, phosphate sponges or whatever we tried. I was still going to feed the fish and that was still producing the nitrates and in turn the phosphates. We moved the stuff to the bigger tank, my feeding habits have not changed, we went to the high nitrate/phosphate readings just until last week. The feather caulerpa really started taking off and the phosphate readings went from 5+ to under 2 and are continuing to improve. The nitrate readings are about 5. I am totally convinced it has to be the refugium. My sandbed is very deep, not very live I am sure. But who can afford to put a couple hundred pounds of live sand in a tank? The little bit of live that you culture with will take forever to grow to the point of being useful ... at least that was my experience in the other tank.

A DSB will aid in the reduction of nitrates after some time as I am reading about also...What I am gathering so far is. a 6" DSB is no more efficient than a 2" SB without the use of a plenum or dead water space under it for anaerobic bacteria to utilize the nitrate and convert it to nitrogen gas which goes into the atmosphere..again, this is read and not practiced by me yet. I have read nothing in published material, that states to just dump sand in the tank and expect it to control anything...Now with that said.

I had a bad Nitrate problem and have yet to buy Corals for that reason...I believe mine were in the 150 to 200 range...I am suprised the crabs and snails even lived...

I have as follows...

55 gal
110 lbs LR
3 inch SB
No Filtration
Sealife Systems ps75 Skimmer
Sump used as water holding and return to house the skimmer
2 Penguin 1140 300 gph PHs
CAP 1800 Sub Pump for the return
I do run a prefilter sponge on the overflow ( gets rinsed out daily)

I have managed to get my nitrates down to 5 to 10 ... ( Thanks to Mark for the suggestion of getting rid of all fiter media)

I don't know where the nitrates are going but they have lowered greatly since the absence of filter media....

[maiceman]

hhhmmmmm... my sand took only a few days to start showing worm trails and I had the bubbles on the glass in a couple of weeks. My DSB was brand new Southdown about 3.5 inches deep seeded with a cup of sand from a friends tank. According to Dr. Ron the bugs are very prolific at reproduction. If you bought live sand you really are not getting the infauna needed, you just get wet sand with bacteria. Everything I have read suggests buying a seeding kit or getting a cup of sand from an established tank.

I am interested in the refugium success though. I think I am battling phosphates as well and will verify as soon as I pick up a new test kit. I have been looking very closely at RO/DI systems to remove them from my tap water but I have been using PO4 absorbers till I can fork over the dough. Maybe a refugium is a better way of attacking them... but I don't know.

What does everyone think?

[reefrunner69]

I know the LR will handle the conversion of ammonia/nitrite just fine and the DSB will take care of the nitrates

LR will take care of nitrates as well. The nooks and crannies of the LR contain facultive bacteria that convert nitrate to nitrogen gas, just as the lower levels of a DSB. A DSB is also responsible for the conversion of ammonia and nitrite. Here is the kicker though, the DSB will not convert the nitrate caused by the LR and the LR will not convert the nitrate produced by the DSB. The reason...proximity. When the nitrate is formed (in whichever media) it is in proximity to the facultive bacteria responsible for converting nitrate to nitrogen gas, and it is done immediately (or most likely not at all).

What about a FO tank with very little rock and a couple of Emp 400's with bio wheels or a wet/dry? Would a DSB control the nitrates in this type of tank?

To an extent, because the DSB would also be responsible for the majority of the nitrification. In a system described like this, IMO, the nitrates would never be 0.

Wouldn't it be better to use a smaller pump to slow water flow through the skimmer body?

If it is a venturi driven skimmer, then the pump has to be able to drive the venturi efficiently enough to provide enough bubbles. This only occurs with larger pumps (comparably). You are also interested in turnover. You want to process a minimum of 1 tank volume per hour, prefferably more. In order to do this with a "small pump" (comparably speaking) the skimmer would have to be huge.

When the nitrate is formed (in whichever media) it is in proximity to the facultive bacteria responsible for converting nitrate to nitrogen gas, and it is done immediately (or most likely not at all).

Huh? we are talking about an enclosed system in which the water has no choice but to be moved over and around the bacteria that converts it. So it causes me to how that statement is scientifically possible, or maybe you just confused me . Depending on how much you feed or introduce nitrate forming substances into the tank will depend on how much the nitrate factor will rise or fall. the bacteria that converts this doesn't just give up and stop working.

[reefrunner69]

we are talking about an enclosed system in which the water has no choice but to be moved over and around the bacteria that converts it.

But it does. The facultive bacteria are in areas of very low waterflow. It is the proximity (closeness) of the nitrification that allows efficient denitrification. Once the nitrate has moved into the watercolumn, it is unlikely that it will make it's way to the denitrifying bacteria. Think of it as the nitrosmnas and nitrobacter actually handing the nitrate to the denitrifying bacteria. Since the nitrifying bacteria will have no use for the nitrate (they're looking for ammonia and nitrite) they cannot pass it along to the denitrifying bacteria.

[loganj]

OK, that makes sense to me. For some reason, I had the idea that the nitrates in the water column were being converted by the DSB. What you're saying makes a lot more sense. I guess a DSB would benefit the FO tank to an extent by processing both ammonia/nitrite and nitrates. Since I don't think this guy is gonna add any more rock to this tank, and it already has a CC substrate, I guess the only way I can control the nitrates is with water changes and some sort of absorbing resin. I'll only be there every two weeks and I don't want the nitrates going crazy between changes. I wonder how a thick layer of sand would do over the CC or would the CC have to be removed first?
In reference to the skimmers, here is an example. Take a Berlin that is recommended for use with a Mag 5. I read in another post that one had been used with a Mag 7 and even a Mag 9.5. That was really what I was wondering...whether oversizing the pump would push water through the skimmer so fast that efficiency was lost due to the reduction in contact time. Guess I should have been more clear on the original question.
Logan J

[reefrunner69]

I wonder how a thick layer of sand would do over the CC or would the CC have to be removed first?

IMO, the CC should be removed first. The sand will end up under the cc rather than ontop. Provided there was appropriate fauna in the sandbed and care was taken not to introduce fish harmful to the sandbed, the tank would benifit from a DSB.

Take a Berlin that is recommended for use with a Mag 5. I read in another post that one had been used with a Mag 7 and even a Mag 9.5. That was really what I was wondering...whether oversizing the pump would push water through the skimmer so fast that efficiency was lost due to the reduction in contact time

First let me say, Red Sea recommends the use of a Mag 7 with the Berlin Classic. They say a Mag 5 is not sufficient to drive the venturi properly (from your experience I would say that is not the most accurate statement they have made ) IME, I used a mag 7 with the berlin for awhile, but when I upgraded the pump I got more skimate. Go figure.... I think there comes a time when if there isn't sufficient waterflow through the skimmer you are only scrubbing a small portion of the tank water.

[loganj]

OK, I was going on advertisements (Dr Foster catalog, I think ) that said a Mag 5 was recommended. Since that's what the Berlin skimmers I have used had, I just assumed that was correct. You know what happens when you assume though...make an *** out of U and ME . I guess if one of the Mag 5's dies, I'll replace it with a 7.
As much as I love to fool with aquariums, it sure is a pain to have to come behind someone after they've already set it up all wrong and try to fix it. Especially when they are unwilling to spend anything to correct the problems. I guess that goes with it though.
Logan J