# 10 gallon: Danios dead after 50% water change



## arul (Mar 11, 2014)

Last night, I changed half the water in my 10 gallon Walstad tank. This morning, both the leopard danios were dead and on the surface. The ramshorn and malaysian snails are alive, but on the top. The danios have red marks from the eyes to the tummy and one has a bloated tummy.

I did the water change only because the water was yellowish, but the danios were okay prior to the change. The water hasn't been changed for about 2 months, but I've topped it regularly. There are two airstones and it's planted with anacharis, moneywort, ludwidigia repens, rotala rotundifolia, java ferns and java moss.

This is not the first time there's been fish deaths after a big water change. A few months back, I changed about 40% water in my 20 gallon Walstad tank and two danios died soon afterwards. Prior to that, water hadn't been changed for months, only topped off.

Whenever I change or top off water, I let dechlorinated water drip at a higher level into the tank using a long airline tube.

Is there something about a large % water change that alters water chemistry drastically to the extent of killing fishes?


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## pandragon (Jul 10, 2014)

Fish tend to get used to levels of chemicals in the water, ferts, toxins, bacteria, etc. It is possible that doing a big change changes the levels of everything in the water enough to stress the fish to death. Also, make sure there is no chloromine in the water you are using or use something like seachems prime to dechlorinate the water. I am not entirely sure if the ammonia that is 'locked up' by prime can turn back into a toxic state or not before the plants use it up or not. The red streaks could be nitrite poisoning, which isn't typically in tap water, but you could check the nitrite/nitrate/ammonia levels in the tap water just in case. 

I hope your fishies don't keep dying. Maybe do smaller water changes over a week would be better than a %50 once in a long time?


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## arul (Mar 11, 2014)

pandragon: Thanks! I'll try smaller water changes next time. Prior to adding the fish 2 months ago, this tank had a high level of nitrite for a week or so. But it got resolved later.

I've also used Topfin dechlorinator since last September 2013. I just bought a new 500ml bottle of Prime which I've not used yet. I should start using Prime; it appears to be more useful than Topfin, which only removes Chlorine and Chloramine.


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## pandragon (Jul 10, 2014)

I am not sure if Top Fin actually removes the chloromine like prime does or if it just removes the chlorine part and leaves the ammonia left over. I don't trust anything TopFin branded, except maybe there tanks which can be resealed if necessary.


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## MattArmstrong (Aug 17, 2014)

arul said:


> This morning, both the leopard danios were dead and on the surface. The ramshorn and malaysian snails are alive, but on the top. The danios have red marks from the eyes to the tummy and one has a bloated tummy.


I'm sorry it seems like you've been through this twice!

I think pandragon is on the right track. The symptoms above are consistent with ammonia poisoning (e.g. red streaks on the body, weird snail behavior), and Top Fin dechlorinator does not claim to neutralize ammonia.

Your tap could have ammonia in it straight out the tap. More likely, your tap could have chloramine in it. Disturbing stuff in the tank such as the substrate (often done with water change) can also stir up sources of ammonia. Regardless of how ammonia was released into your tank, Topfin dechlorinator does not claim it neutralizes ammonia. It may be that your tank's bio-filter or plants can absorb it within hours, but the ammonia spike is still happens.

Products like Amquel and Prime take care of ammonia, nitrites, some metals, etc.

More info here: http://www.fishchannel.com/fish-health/healthy-aquariums/water-conditioners.aspx

In particular, the article talks about "simple" dechlorinators like the Topfin one you've used, being okay in certain circumstances.



> *Partial Water Changes*
> If properly managed, a weekly 10- to 20-percent partial water change is not a problem with water containing chloramines. Many hobbyists use automatic water-changers or garden hoses to conduct partial water changes with untreated replacement water flowing directly into the aquarium. Before starting aquarium maintenance, turn off the filter and unplug the heater. As the water enters the aquarium, slowly drip water conditioner into the aquarium. After turning off the tap water, swirl the aquarium water with your hand to mix the water and conditioner. Reconnect the heater and plug in the filter. The instantly neutralized chlorine is no longer a threat, and the small amount of ammonia introduced will be consumed by the enormous bacteria colonies living in the filter and substrate.
> 
> I safely do up to 50-percent water changes in aquariums containing only a couple of larger fish, but these aquariums have massive filtration capable of quickly eliminating the ammonia left over from the severed chloramine bond.


I would guess that a Walstad tank (little or no filtration, etc.), might be more vulnerable. In those tanks the plants compete with the bio-filter for ammonia quite successfully. So, the bio-filter may not be as robust in your tank as the one in the large Cichlid tanks mentioned above. You also mentioned changing water the prior night. I am no expert on how plants consume ammonia, but I would not be surprised if they were better at consuming it when the lights were on...turning the lights off may reduce your tank's ability to remove ammonia from the water.

So I'd:


Use Prime from now on, like you plan to. In fact, I've taken to squirting some Prime into the tank at first sign of fish distress if I have recently disturbed the tank.
Prefer more, smaller, water changes. Especially if there is no emergency you're addressing with the change, and especially if the tank has not seen a water change in a long time.
Prefer doing major maintenance at a time when you can observe the tank for an hour or two afterwards.


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## arul (Mar 11, 2014)

pandragon said:


> I am not sure if Top Fin actually removes the chloromine like prime does or if it just removes the chlorine part and leaves the ammonia left over. I don't trust anything TopFin branded, except maybe there tanks which can be resealed if necessary.


pandragon: Thanks! I'll be using Prime from now on. There's a little Top Fin dechlorinator left, but I'll just put it away.


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## arul (Mar 11, 2014)

MattArmstrong: Thanks for the detailed info! Very useful and I really appreciate it.



MattArmstrong said:


> I'm sorry it seems like you've been through this twice!
> 
> I think pandragon is on the right track. The symptoms above are consistent with ammonia poisoning (e.g. red streaks on the body, weird snail behavior), and Top Fin dechlorinator does not claim to neutralize ammonia.
> 
> ...


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## digital_gods (Apr 23, 2010)

I've had best of success using Prime. Seachem makes a dry version of Prime called Safe. LFS don't like to sell it because it last a long time so your repeat visits are fewer. If you decide to go with a R/O system, you need solid carbon block to catch the chloromine. Bulk Reef Supply has good prices.


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## arul (Mar 11, 2014)

Thanks! I never knew there was a powder version of Prime. You'll need very small spoons to dose the water with Safe; it is very concentrated.



digital_gods said:


> I've had best of success using Prime. Seachem makes a dry version of Prime called Safe. LFS don't like to sell it because it last a long time so your repeat visits are fewer. If you decide to go with a R/O system, you need solid carbon block to catch the chloromine. Bulk Reef Supply has good prices.


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## aquariumlover10 (Oct 15, 2014)

Ami the only one that thinks the reason is because leapard danios need a 30 tank? I would try white clouds if you want danios.


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## SBS (Feb 26, 2013)

I'd suggest test your Ph before and after a water change. Also your Kh. My suspicion is your tank water has become acidic and your tap brings the Ph/Kh back up rapidly upon water change. It's what happens when one doesn't do water changes regularly. Tank and tap differ by a lot.

Another thing I'd like to mention is that once fish are subjected to high spikes of ammonia/nitrites, they don't last long down the line. They don't normally die immediately, especially not fish like danios but their immune system gets affected and it takes its toll. They drop dead by the minimum of things afterwards.


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## TropTrea (Jan 10, 2014)

What your describing is why I never do large 50% water changes. Even using RO water I will not change more than 25% of the volume at one time. Normally I try to do 10% water changes every other day but at the absolute worst case 10% once per week. 

As other mentioned fish can get used to different water conditions if the change is gradual. Danio's are rugged fish and have a broad range of adaptability. But when you do a large volume water change your creating a sudden change in conditions that can shock there systems. 

There can also be other factors involved here like something in your tap water. Yes chlorine and chlorinates are common from municipal water sources. But these are not the only issues in some areas. Check your water for pH, Phosphates, and hardness. sometimes simply aging the water before use will help if the impurities can be released as a gas over time. 

However I strongly recommend the investment in a RO system, especially if someone has a large tank or multiple tanks. You don;t have to get a huge system but get one that will produce at least 10% of your tanks volume in 24 hours. With enough storage space for water that is produced in two day. This will allow enough water for a 10% water change every other day and also give you a reserve for an emergency change of 20%.


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## barrel (Dec 31, 2011)

nano tanks are more affected by imbalances

when using dechlorinaters, also use a test kit to make sure the chlorine is really zero


2nd the RO, can always periodically add some flourish to RO that sits


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## arul (Mar 11, 2014)

aquariumlover10 said:


> Ami the only one that thinks the reason is because leapard danios need a 30 tank? I would try white clouds if you want danios.


No, these leopard danios are the same size as regular zebra danios. They all go well in my 20 and 10 gallons. Right now, I'm using the 10 gallon tank for guppy fry, and the adult guppies and danios are in the 20 gallon tank.


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## arul (Mar 11, 2014)

I'll test the pH before the next water change and the pH of the newly dechlorinated water. I'll do a 10% change tomorrow. The average pH in my water before a change is usually 8.0 to 8.2. I'll also test for ammonia and nitrites more regularly. Thanks.



SBS said:


> I'd suggest test your Ph before and after a water change. Also your Kh. My suspicion is your tank water has become acidic and your tap brings the Ph/Kh back up rapidly upon water change. It's what happens when one doesn't do water changes regularly. Tank and tap differ by a lot.
> 
> Another thing I'd like to mention is that once fish are subjected to high spikes of ammonia/nitrites, they don't last long down the line. They don't normally die immediately, especially not fish like danios but their immune system gets affected and it takes its toll. They drop dead by the minimum of things afterwards.


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## arul (Mar 11, 2014)

TropTrea said:


> What your describing is why I never do large 50% water changes. Even using RO water I will not change more than 25% of the volume at one time. Normally I try to do 10% water changes every other day but at the absolute worst case 10% once per week.


Yup, I'll stick to 10% at most. Thanks.


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## arul (Mar 11, 2014)

barrel said:


> nano tanks are more affected by imbalances
> 
> when using dechlorinaters, also use a test kit to make sure the chlorine is really zero
> 
> 2nd the RO, can always periodically add some flourish to RO that sits


I'll try to keep the dechlorinated water in the bucket longer before adding it to the aquarium. Maybe an hour or so. Adding the RO would mean I'd have to add ferts later on? That defeats the purpose of a Walstad tank, right? Thanks.


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## arul (Mar 11, 2014)

Here's an update. I now have about 20+ guppy fry in this 10 gallon Walstad tank. I did a 10% water change yesterday. The new water was tap water treated with Prime. I waited for about 15 minutes before adding the water to the tank. The guppy fry are all doing great.

Thanks all, for your help.


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## pandragon (Jul 10, 2014)

The guppies are doing great, but the danios died? Did you have the guppies and danios at the same time or were the guppies replacements for the deceased fish? I know guppies, and all common livebearers like mollies and platys, like harder water than some other fish. Maybe, the water was just too hard for the poor danios or the difference in hardness caused by the plants sucking up carbonates and other minerals and the amount in the tap water was great enough to mess up there osmoregulation? Hopefully sticking to the 10% water changes will keep all inhabitants healthy and happy, and congrats on the guppy fry!


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## arul (Mar 11, 2014)

Oh, the danios died when they were the only inhabitants of this 10 gallon tank and after I did a 50% water change. After a few days, when everything looked okay, we transferred a few fry from the 20 gallon tank to this 10 gallon tank. And later, a pregnant guppy, she gave birth to around 12 fry there. We moved her back to the 20 gallon tank after that. The last 10% water change was on November 17th (it's 22nd today), and the fry are doing great. Here's a photo.


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## TropTrea (Jan 10, 2014)

arul said:


> I'll test the pH before the next water change and the pH of the newly dechlorinated water. I'll do a 10% change tomorrow. The average pH in my water before a change is usually 8.0 to 8.2. I'll also test for ammonia and nitrites more regularly. Thanks.


That is very alkaline for most fish. I keep my tanks always under 7.2pH and right now I have 7 different varieties of live bearers. Yes some live bearers can handle harder water up to 8.5 but guppies like it a little more neutral. When you get to Danio they prefer it slightly acidic to neutral 6.6 to 7.2. But they are considered a hardy fish so unless your breeding them change in pH is worst than high pH.


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## arul (Mar 11, 2014)

TropTrea, I should look into adding driftwood in my tank and bringing down the pH. I used to have ghost shrimp earlier, and they survived well. Thanks.


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