Tropical Fish Forums

[Topper]

Quick recap:
Changed the main filter in a 29 gal/110 litre in late August (was a Biowheel 280) to a Fluval 205 Canister. There is an internal secondary filter that has a 125 gph flow rate and has never stopped running. The Fluval is set up with peat pellets, old floss media from the previous filter and the new chips. The tank has all small fish (8 cories, 8 neons, 8 WCMM and 4 otos) - all very easy fish. 20% to 25% WC every week, sand bottom with live plants and some driftwood. There was no mini-cycle to speak of when I changed the filters.

The issue:
I test the water two to three times per week (new filter) and on the sixth (sometimes seventh) day there is a slight reading of ammonia (I would guess about .1 to .15 ppm). Obviously I change the water and it falls to 0 with the Prime I use for WC's. The part that puzzles me is that the nitrates are 20 ppm (falling to about 10 after WC) and this has been pretty consistent since I set up the tank two years + ago with both filters. I would sometimes miss WC's with the old filter and even after two weeks there was no ammonia.

The question:
Where is the ammonia coming from? Is the Fluval 205 not enough to handle even such a small bioload? There is obviously a healthy bacteria colony (consistent nitrates). Do I have the baskets in the filter set up incorrectly? Should I adjust the flow from wide-open to a little less?

I don't like any ammonia in an established tank. I don't understand why there would be any with a healthy bacteria colony in two filters. Any experience or advice would be greatly appreciated as this is worrisome and I want to avoid any potential problem.
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[diademhill]

Could it be a bypass in the filter? - water flowing the path of least resistance so it is missing the media?
I would try a foam cut to fit one of the baskets. It needn't be thick and could be topped with other media.

[Topper]

That sounds quite plausible and also makes perfect sense. I will redo the filter set up and add a piece of filter foam to the peat basket and transfer some floss that is currently in the Betta's tank filter to the ceramic media basket. This should certainly fill in any gaps that may have developed over the past two months and promote an even bacterial colony.

If it weren't for the nitrates and the second filter, I would think that I caused a mini cycle by changing filters. However, I seeded the new filter and never turned the internal filter off and never got even a hint of nitrites.

Thank you, Sue.
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[thatcichlidguy]

That is very odd, could be because the baskets aren't seated correctly and you get some bypass. Still I'd think in an established tank it would need to bypass a lot of water before you saw anything like that especially with two filters running together and a very small bioload. I think you may be having some decomposition issues with the drift wood or plants ,or both. Also when was the last time the sand got turned? Decomposition of plant matter in the sand is the same as on top of it, maybe worse since you don't see anything. Rotting vegatation in the substrate can build up and cause some nasty headaches like this. Sand substrates really need to be stirred up from time to time particularly if the bed is fairly thick.

First thing I'd do is check the wood for obvious rot. If it's rotting then out it goes. then I'd snoop around for anything else that could cause decomp in the tank and stir the sand up (as much as is reasonable that you don't up root your plants) in sections , one per waterchange. Hopefully that will lead you in the right direction.
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If everyone's thinking alike then no one is thinking.

[Topper]

[thatcichlidguy]

Maybe it has something to do with the peat in the Fluval. What gets me is that it's a slow build up . Theoreticly the BB should grow their colony to compensate for this and you should never any jump in ammonia. Especially since this is an established tank. Might be worth taking the wood out for a week just to see what happens if the problem persists.
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[Topper]

WC yesterday. Slight (very) ammonia reading - just a hint of green right before WC. No ammonia all week until yesterday.

Filter baskets are reconfigured and the driftwood is out for now (along with the Java Moss that was growing on it ). I inspected it and there doesn't seem to be any rotting or soft areas. Better safe than sorry.

Nitrates have also stayed below 10 all week. Very odd stuff.
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You're gonna need a bigger boat...

[thatcichlidguy]

Too bad you had to remove the Java moss . Could be an internal rot in the wood. Had it happen to me before. The wood was fine on the outside and rotten in the middle. Hard to imagine anything else that could cause this given the circumstances.
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If everyone's thinking alike then no one is thinking.

[Topper]

Unbelievably, it happened again. Slight ammonia reading before water change. I ended up changing about 40%. Nitrates 10 and Nitrites 0.

I just don't get it. A small bioload with two filters on such a small tank should not present this sort of issue. The plants are trimmed, the baskets in the filter are reconfigured, the driftwood is gone and the tank is well maintained. Could there now be an imbalance with the new filter and the small internal filter? Maybe there is no bacteria in the larger Fluval? The nitrates seem to contradict this, but it is my only guess. Could there be too small a bioload?

I'm at a loss on this one and I'm ticked off that I lost all of the Java Moss on the driftwood that was so thick and took so long to fill in.
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You're gonna need a bigger boat...

[unissuh]

What test kits are you using for ammonia and nitrate? I thought that Prime didn't affect ammonia readings for most test kits.

Also, how heavily is the tank planted, what sort of lighting do you have and do you fertilize? If there was no nitrate reading I'd be tempted to speculate that maybe the tank is basically not cycled and the plants are just sucking up all of the ammonia as it is being produced. Towards the end of the week perhaps you run out of a macro/micronutrient which slows down nitrogen uptake therefore you get a slight ammonia reading. Waterchange replaces nutrient, nitrogen uptake speeds up until it is depleted.

I don't think you need to worry about surface area in those filters, theres heaps of space for bacteria to grow throughout the tank. Doesn't have to be in the filter.

It does sound pretty weird though, I can't really think of a logical explanation.
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