Creeping Nitrites

[mgav1975]

I was looking for the answer to why my nitrites keep creeping back up to 0.2. My anonomes and star fish seem to suffer as result. My pump is moving about 1000gallons hr on a 150 gallon tank - I'm guessing aprox 6.7 turns an hour. I have a standard wet dry set up with a dual hose prefilter skimmer box. The sump was supposed to be rated for a 220 gallonm tank aprox 32in long 16 in wide. I am using 2 strandard 1in "u tubes" to remove water from the tank. Any idea how many gallon per hour they reomove? What size return pump can I put on the tank without emptying out my sump before it can fill.

[leebca]

WELCOME TO REEFLAND!

We'll need additional information, such as:

Do you use live rock? About how many pounds in the system?
Do you have a substrate? deep sand bed? or ? How deep is it?

For the 150, you need about four or five times the overflow opening space as what you've described in each of two corners (about 9 times what you've provided for). The flow rate will need increasing. Assuming you use live rock, two internal pumps are needed too, unless you didn't mention what you have.

Until the overflow tubes/openings are modified, the return pump won't do a lot of good. You may be 'stuck' with a very under pumped system if you stick with those overflows.

[mgav1975]

Let me provide a bit more info. I have apox 50-60 pounds of live rock and 2in of DSB. My ammonia and nitrates levels have always tested ok. I have a protien skimmer and UV sterilizer and a small pump with wave maker thing. PH is 8.2. Salinity 1.020. My nitrite do seem to come down but any time I add anything it comes back up. Over the last few months I had been making several mistakes that were likely disrupting my biological filtration. For example vacumming my sand bed and changing 20 gallons of water a weeky. Changing the position of my return hose disrupting my deep sandbed. Adding 15 lbs of uncured live rock with heavy vegetation growth to my tank at a time. I believe that this through my tank back into cycling. I have corrected these errors over the last 6 weeks and my tank seems to be stable for the most part. I have been feeding sparingly as well.

Getting back to the my filtration.... my overflow system consist of 1 skimmer box with 2 big "pool hoses" leading down to the wetdry. I have 2 standard over flow tubes, obviously not enough. How many GPH do the standard overflow tubes provide. I am thinking of adding another pump to my already crowded sump but dont want suck it dry faster than the over flow can remove water from the tank. Is that something I should worry about? I think there may be room to squeeze another over flow tube in there? Is there a larger size over flow tube on the market? Adding another skimmer box would be difficult.....how would it connect to my wetdry it only has a spot for the 2 existing hoses? As always thank for the advice

[leebca]

Thanks for the additional information.

For a marine system for FOWLR (which is this forum) it is usual to have about 1-2 pounds of live rock per system gallon.

Two inches of substrate is not considered a deep sand bed (DSB). Usually a DSB starts at about 4 inches and ranges up to 6 depending upon the substrate material. Two inches is a bit in the no-man's zone when it comes to substrates.

Water changes should not affect the biological filter either negatively or positively, if you perform water changes 'normally.' See: How to Make a Successful Water Change

Cleaning the < 2" substrate should be routine about once a month. If it is a 4" or deeper sand bed in the main display with a high fish load, the debris and detritus is siphoned off from the top half inch or so, monthly or each tiime you do a water change. If you haven't been doing this, then there will be a build up of waste. The amount depends upon how many and the kinds and the sizes of fish and other nitrogen waster producers you are keeping. If you haven't been cleaning routinely, then a sudden large cleaning can upset the system quite a bit. In cases where people have let it go, the thing to do is clean about 25% of the substrate every other week until it is 'caught up.'

I'm unsure how the changing of the return hose would upset the substrate bacteria. I won't say you have been misinformed by this action since I am unsure what actually changed. Bacteria on the live rock and other internal surfaces need water flow to do their job.

Adding live rock to an establish marine system is generally not something you want to do, especially if that rock has not thoroughly been cured. That can create a lot of problems with the biological filtration -- usually by overloading the system with die-off from the new LR.

Regarding the total flow rate: The total flow rate to aim for is about 8 to 10 times the system volume, per hour. The flow rate is both the return pump and internal power heads.

For that size aquarium, there should be at least two overflows located apart from each other (one in each corner) to get the full effect of removing surface water. The U-tubes you're using are inadequate and can't supply enough return water, even if you added more.

There is a formula and I don't have it handy, which can tell you the gravity flow of a pipe using the diameter opening of the pipe (or tube). I'm traveling and don't have that with me and I didn't commit that to memory. But I can tell you this, the opening of each of the two overflows (one in each corner like I just described) would be rectangular, measuring a minimum of about 6 inches long and 4 inches wide. This 'box' would be tall to nearly the inside height of the tank. The water would cascade over this top opening of the box and fall into a pipe opening in the bottom of the aquarium about 1.5" in diameter. Remember this is doubled. These two pipes then lead to the sump. Your return pump would be pumping back into the aquarium about 1000-1200 gallons per hour at the head pressure of the system. Then, there would be at least two inside power heads pumping each no less than 200 gph to create flow inside the tank to keep the waste moving around and some going through the overflow.

The above would be a minimum. More flow can be added either inside, the return pump, or both.

Now, to the wet-dry. It is unclear why you are using a wet-dry. You've sort of mixed two biological systems. You have a shortage of rock, a substrate that isn't deep, and now a wet dry to perform biological filtration. This can all work together, but the flow must be increased considerably.

This system would have an average biological load ability and should support about 30 inches of 'average' stocky fish. Is the system overloaded? See this: Fish Stocking Limit - for FO and FOWLR

You do have to worry about how much water the overflow pipes will carry away by gravity to make sure your return pump doesn't pump water in faster than it 'falls' out.

The overflow U-tube siphons you are using would probably do okay for a 30 gallon or smaller aquarium. When you get into larger aquariums you want to shift the overflows to be more like the corner boxes I explained above. The bottom corner of the display has a hole drilled into it that connects to the 1.5" drain pipe. The tallness of the corner box limits how much water can overflow and keeps the tank level fairly constant.

You should consider getting a book or two for guidance on marine system setups. Check this list out: Marine Aquarium Books & Reading You'll find good details in a book and diagrams that I can't provide you here.

I hope the above has helped.

[mgav1975]

Thank you for taking so much time and all of the good information. I did some research regarding my overflow box and U tubes and it is similar to the one you described measuring 6x9in. The system I am using removes aprox 1200 gph according to manufactuer. My return pump is rated for 1000 gph. I figure I have about 30 in of fish( mostly tang shaped though) I have avoided placeing power heads inside my tank in order to accomodate for my shark's sensitivity to electric current. My plan is to add some sand, improve the flow over my rock, very slowly increase my amount of live rock. I am going to consider either placeing a bigger return pump in my wet dry or adding another smaller wetdry.