Might have crashed my system... - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 10 Old 01-25-2013, 08:46 AM Thread Starter
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Might have crashed my system...

Recently turned my 72 gallon into a discus tank.

6 juvies, between 2.5" and 3.5". Knew about the sensitivity issues due to size, felt up to the challenge as I have been keeping fish for years, including breeding three species of ACF, axolotls, and angelfish.

Other stocking includes 6 threadfin rainbows (was 7, one jumped out of the net during substrate change and was found too late), 6 sparkling gouramis and 1 german blue ram.

The other day I made the move to change my black sand to play sand. That is when the trouble began.

Yesterday, a day after the change, one of my 2.5" discus died, readings were Ammonia 0, Nitrite 0, Nitrate between 0 and 5. The tank had received a 100% waterchange during the substrate change. The tank had been getting multiple water changes weekly since the discus had been added anyways.

This morning my GBR is sitting on the sand, breathing alternating between fast, labored and slowing.
Tested the water and was between 0.5 -1.00 Ammonia, 0 Nitrite 0 Nitrate.

I did a large water change.

I am panicking. I fear that yesterday when I filled up the tank from the tap and treated with Stress Coat that I did not give the Stress Coat ample time to spread and may have turned the filters on too soon, sucking up non treated water. Could I have wiped out my entire filters?

Panicking is probably putting it mildly. I am full out freaking.
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post #2 of 10 Old 01-25-2013, 08:55 AM Thread Starter
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Also, tank has been set up a few years. Two Fluval 405s on it, moderately planted low tech system.
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post #3 of 10 Old 01-25-2013, 08:59 AM
You removed most of your bacteria from the system when you removed the substrate. Your system will now go through a cycle. Need to throw in some Ammo Lock or Bacteria to eat up that Ammonia. Or keep doing large water changes, until the system catches up.
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post #4 of 10 Old 01-25-2013, 09:17 AM Thread Starter
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Thanks, will have to monitor closely.

The discus have been out and about, swimming and ate bloodworms for me as usual. Fingers crossed I can keep the damage to a minimum.
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post #5 of 10 Old 01-25-2013, 09:23 AM
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Originally Posted by jenste View Post
Recently turned my 72 gallon into a discus tank.
The other day I made the move to change my black sand to play sand. That is when the trouble began.
I know this is after the fact and will not help the current situation... I cannot help much with that.

I would have expected that in an established tank a substrate change would have been done in parts. Messy, but safer for the fish.

Is your replacement water of the same parameters as your normal tank running water other than perhaps the chlorine? A 100% change is pretty heavy for an established tank even without the substrate change, particularly if the water is different enough... it could be quite a shock to sensitive fish. Apparently this is likely the first issue as your initial contaminant readings are fine with zeroes across the board.

I think that all you can do is keep testing and changing water to keep the nasty's as low as possible until things settle out. Sadly, I expect that you may lose more fish in the process.

I assume that a large water change is 50%... seeing as 100% was an issue I would expect that you should keep it no more than 50%.

What did your other parameters test (GH, KH, pH) from the tap compared to the tank before the substrate change? Can you retank some of the fish to get the ammonia production down some?


Total years fish keeping experience: 7 months, can't start counting in years for a while yet.

The shotgun approach to a planted tank with an LED fixture

Small scale nitrogen cycle with a jar, water and fish food; no substrate, filter etc
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post #6 of 10 Old 01-25-2013, 09:39 AM Thread Starter
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Since getting the discus juvies I had been doing 50-75% water changes daily as encouraged on discus groups. I assumed, perhaps wrongly, that the 100% wc would be handled fine as they had been accustomed to large wc's daily.

After a 100% wc I would have been shocked if the readings had NOT been nearly 0 across the board! Seeing a bit show up for nitrates seemed normal to me at the time for being a day later. However, anther day later with ammonia showing in tests I was a bit surprised.

I had done a 40% water change approximately this morning and was going to do another this evening depending on the test results.
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post #7 of 10 Old 01-25-2013, 09:49 AM
Oh nono. 75% is too big, it will slow the re-cycling process and create fluctuations if you change out too much. Please limit wcs to50% or lesd.
Good Luck!
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post #8 of 10 Old 01-25-2013, 12:03 PM
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I'd get some Seachem Prime water conditioner and use that to detoxify ammonia and nitrites while you're getting your tank established again.

I hope you don't lose any more fish. Good luck and welcome to the forum.

Animal testing is a terrible idea; they get all nervous and give the wrong answers.
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post #9 of 10 Old 01-29-2013, 05:47 AM Thread Starter
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Thanks. Seems to have restabilized. No other losses and readings are back to where they should be. Mini cycle from removing old substrate + having filters off for a few hours while changing out + 100% new water.

All else is well in the tank
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post #10 of 10 Old 01-29-2013, 11:42 AM
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Problem seems to be resolved now, which is good. I don't think there can be much doubt but that the issue was ammonia. The reading of 1ppm is going to severely stress fish like rams, discus. Daily major water changes to dilute this is the only solution, which you did, and using a conditioner that detoxifies ammonia and nitrite as Romad suggested is advisable unitil things are back to normal.

On the substrate change, I have done this many times (in fact I am going to be doing my 70g today) with never a rise in ammonia or nitrite. Well planted, and especially floating plants, should handle this. Plus, keeping any wood/rock/decor from the established tank in tank water [I put this either in with the fish in their temp tank or with the plants in a container of tank water] and transferring these items to the new setup will move over a lot of bacteria. If plants are minimal, using a bacterial supplement can help.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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