Migrating tanks, nitrate problem

[xrunner123]

I have 2 tanks-

45 gal Reef with 45lbs LR and 2” or so of LS. No sump. Bak pak skimmer.
Not heavily stocked, just some mushrooms and polyps with 3 x 2” fish.
15 small crabs, and a ton of bristle worms.
Used inland aquatics det kit once.
Has been up and running for about 2 yrs.
Nitrates are 0

125 gal FOWLR. 100lb LR, 3.5” of LS. 40 Gal sump. 3 x 3” fish.
15 or so small crabs, 2x8inch cucumbers.
Used inland aquatics det kit twice
Has been up and running for 1.5 yrs.
Nitrates are 30ppm

Now my question is why aren’t my nitrates 0 in the 125gal tank? I do the same scheduled maintenance at the same time. Both tanks use the same RO/DI water. I just measured them with the same kit at the same time.
What am I doing wrong or not doing? The 45 gal tank never ever had a nitrate problem but the 125 always did. When I first set it up, it was at about 80ppm for about 6 months before it dropped.

For a FOWLR tank this is fine, but I am going to break down the 45 and make the 125 a reef. And I assume that 30ppm is not gooooood.

The only thing that I can think of is that I do not have a lot of bristle worms to stir things up? More crabs? I just don’t know. Should I get my nitrates down before I make a switch or should I move all of the contents of the 45 gal to the 125 gal and hope that the nitrates will creep down?

Any comments? What would you do?

Thanks

 

[Anonymous]

Right offhand I see two differences between the tanks (assuming that truly everything else used in stocking is equal). Those are the ratios of live rock used, and the live sand bed. In the 45 you used 1lb/gallon, in the 125 it is a bit shy of this (the calculations require me to use math, I'm not too good at this, so I'll leave it to someone else..heh). You are also using 1.5" more sand in the 125 (depth) than the 45. While I would say that everything I have read indicates that a deeper sand bed would help you with natural nitrate reduction, I cannot come to the conclusion that this is always true.

There is also a six month time differential with the tanks, and the lack of a sump in the 45. Generally, I much prefer using a sump whenever possible, and I couldn't begin to offer a reason as to why or whether or not going sans sump might have an effect on nitrates. However, I do think that if you have had a problem with nitrates with the 125, it might be time to do a single VERY LARGE water change to see if you can knock them down (I'm thinking 50% or better, maybe even 75%). Then I would be curious to know if they stay down, or creep back up.

There are other variables that you haven't listed in your specs, such as l/r source/type, live sand composition, and whether or not there is also a skimmer on the 125. If you want to really get a handle on nitrate readings permanently, then I would suggest researching refugia methodologies as well as best use of DSB's.

Sorry this wasn't more helpful, but I do hope it's given you a direction.

 

[Anonymous]

Oh yes, I would say that, IMO, the presence of a large number of bristleworms might indicate you have a good buildup of detritus for them to eat. What role they might play in your nitrate reading issues I couldn't say.

 

[xrunner123]

Forgot to mension, Turbofloater 1000 skimmer is on the 125.
See what gets me is that the bioload in both tanks are somewhat equal, if not more in the 45. In any event, the bio load in the 125 is nothing. I just have 3 fish. I do a 25% water change 1 mon in both tanks for the past 1 1/2 years. Maybe I should increase it?

Maybe too much sand?

 

[Anonymous]

I don't know about too much sand. The thing is, there are SO many variables that we cannot accurately account for them. For instance, it very well may be that, along with housing a higher density of live rock/gallon in the 45, it may be of higher quality. 25%/month water changes won't change much of anything in the way of nitrates, do a single LARGE w/c and that should have a significant impact. Less sand..well, if you go with too little you won't have the benefit of the anoxic areas where nitrate reduction occurs. The skimmer is a completely different brand, is there a difference in the skimmate quality?

If it were my system, I would do a huge water change, and cure another 25-30lbs. of the best quality l/r I could get my hands on. I would also use more sand to be absolutely certain that I've got anoxic areas for nitrate reduction, as well as set up a refugium and stock it with more live rock and copious varieties of macroalgae (which I would then harvest and sell). While bristleworms (except in plague proportions) aren't a bad thing, necessarily, they are an indicator of detritus buildup, and this very well could be another significant difference. While you don't want this buildup, if it's sufficient to produce good bristleworm growth, they may be consuming it and converting to other more easily converted nitrogenous wastes. A bit difficult to say for certain. (Having been nailed by a very large one in the Caribbean, I'd go with as low a number of bristleworms as possible, it doesn't heal quickly at ALL.)

 

[xrunner123]

Well can I assume that if I transport all of my LS and LR to the 125 that my nitrates will go down?
And I thought that bristleworms are good to stir up the sand.

 

[xrunner123]

anyone else?

 

[Anonymous]

I don't know if that would be an appropriate assumption. As I said, bristles on a small scale can indeed be a good thing. I would do more research into DSB's and refugia if I were you.