What causes illness if water conditions are fine?

[jordzcov]

Hi, Over the past few months ive had a range of issues in the tank. When ive had a major issue ive done water tests which all give fine water readings. A few times ive even taken a sample to the fish store to do more detailed tests, and these also come back fine.

Are there some generic things I should maybe consider or keep an eye out for which can be causing issues in the tank outside of water quality? If water quality is fine, what would be causing fungal diseases in the tank? any advice around this is greatly appreciated.

Details:
70L tank
Now holds 3 neon tetras and 5 Harlequin rasboras

Some recent events:
- Fungus appearing on the top fin of a few of the rasbora

- Some tetras developing large bellys, while others look malnourished.

Brought home new Rasbora which saw 3 tertas already in the tank die, as well as 1 new rasbora die over 2 days

 

[Aiken Drum]

Bacterial infections will just be in the water. Bacteria is everywhere, fish with otherwise healthy immune systems will be able to fight off disease. But if a fish succumbs to a disease, or you introduce a fish with a bacterial infection that disease can then proliferate and infect other fish that would otherwise fight off disease when the bacteria count is low.

Parasites are a little different. They won't spontaneously appear. They somehow have to be introduced into the aquarium. This is most commonly you adding an infected fish into the aquarium, but parasites can also get into your aquarium through food, maybe from driftwood. When people buy new fish, some people just dump the water from the bag into their aquariums, and therefore any infections in the aquarium stores water is now in your aquarium.

Fungal infections are mostly secondary issues. The fungal infection will attack already damaged tissue. So stressed fish, or wounded fish, fish living in poor water quality will be more likely to come down with fungal infections.

Fish are more commonly just being sold with genetic conditions as well. Mass breeding, a lot of inbreeding. Poor husbandry meaning fish are just generally more prone to sickness.

If you are buying lots of fish that are in poor health, consider buying from a different store. Consider a quarantine tank so you are fairly sure fish are healthy before they go in a display tank. And if they arent healthy, issues are more easily seen and treated in QT.

 

[Andy Sager]

Sadly, there are a number of things that cause illness in fish beyond just water parameters. Temperature changes, stressors such harassment, shipping, improper diet, too much light, too little light and improper decorations causing insecurity all can cause illness. Then there are some things that are coming in with the fish such as viruses and genetic maladies that can cause illness. So it's not all and only about the water conditions.

Regarding your fish specifically, the fungus on the Rasbora is a result to an injury. Fungi and bacteria are present in aquariums even under the best of conditions. They are just looking for an opportunity to attack. When a fish gets an injury whether from accidentally rubbing against something or attack from another fish, the injury can become infected if the water isn't clean enough. This fish should be treated in a sterile hospital tank with medications specifically for treating Fungus. ( i.e. Fritz Maracyn Oxy, AAP Nitrofuracin green). The use of botanicals such as almond leaves ,different seed pods or most of this collection : Botanicals will help act as anti bacterials/ anti fungals in the tank to keep wounds from getting infected.
The Neons however are a different story. Sadly many fish from fish farms in Asia carry fish TB or internal parasites. In the case of the fat one, that looks more like an internal worm while the skinny one looks more a case of TB assuming it was not dietary in nature. With TB, it's extremely difficult to treat and to be honest, you will spend much more money on meds trying to treat it than it would cost to buy many new ones. As for the internal parasites, all fish should be given a deworming while you have them in quarantine when you first get them. Medications such as Levamisole HCl or Praziquantel are good dewormers.

It's important, more so today than in decades past, that all new fish go through a quarantine period before being added to the main tank. While in quarantine, the fish gets used to you feeding them, the feeding schedule, lighting schedule, water change schedule and if necessary, being medicated without the stress of being overpowered or picked on by the existing fish in the tank. Without doing quarantine, you invite anything the fish may have on or in them into your main display tank.

Hope this helps.

 

[jordzcov]

As you say, i think its obvious that quarantine is necessary, but how long would you say these needs to be done for? i have had frequent issues with my existing tank, and am still just tryiong to get it up and running and stocked, where it can jsut be left to enjoy.

As a result ive been a bit reluctant to set up a whole second tanka nd all the purchases that go with it, purely to use as a quarantine to add fish once in a whiel or to treat any illness.

is there an 'easy' way to quarantine as opposed to having a whole second tank running constantly?

 

[Andy Sager]

As you say, i think its obvious that quarantine is necessary, but how long would you say these needs to be done for? i have had frequent issues with my existing tank, and am still just tryiong to get it up and running and stocked, where it can jsut be left to enjoy.

As a result ive been a bit reluctant to set up a whole second tanka nd all the purchases that go with it, purely to use as a quarantine to add fish once in a whiel or to treat any illness.

is there an 'easy' way to quarantine as opposed to having a whole second tank running constantly?

I realize that people do not like to have that " extra" tank there doing nothing when they are not adding fish frequently but the reality is this: There are parasites in the aquatic world that have a 90- 110 day life cycle. So any time you quarantine for less than this, you open your main tank to the POSSIBILITY of having a parasitic problem much worse than every day Ick. When it comes to new fish, most bacterial, fungal and external parasite issues happen in the first 7-10 days on average. ( Sometimes shorter, sometimes a bit longer.) If it were me, I would ask wherever I got my fish from if they have dewormed the fish you are buying. If they said "No", I'd deworm them in a hospital or quarantine tank. ( Preferably a hospital tank as this should be a clean sterile container with no substrate so you can see if the fish expel anything other than poo.) This is a type of medication that parasites do not usually form a resistance to unless it is used in lower dosages than directed. I would not " preventatively" treat for bacterial, fungal or external parasites until they are confirmed to be present. Since you only have a small tank, you are not going to have larger fish to deal with so something like a 37/38L tank can suffice as a quarantine tank.
One way of not having to have this tank running constantly is to have a spare filter ( inside corner filter or sponge filter) running in a clean tank so that it gets the nitrifying microbes in it and when you know you are going to be getting new fish, place that filter into the quarantine tank so that you do not need to be concerned with cycling the tank again. Here's the " catch" tho with your situation, you do not have a clean tank to run a filter in to use in a quarantine tank. When your display tank no longer has sick fish in it for an extended period of time you will, but not right now because anything that's in your main tank would then be transferred to your quarantine tank with the filter and definitely hurt any new fish you get as they will be their most stressed as a new addition and stress is what weakens the fish and prevents them from warding off diseases. So for now, to properly quarantine your new fish, you will need to set up this quarantine tank with all new equipment ( use nothing from your main tank or that has been in your main tank) and cycle it " fish less" style. Once this is done, you can add fish to it that are going to be going into your main tank after the quarantine period. After they are in the main tank and showing no signs of anything wrong, you can either break down the quarantine tank and store it, keep it running with an ammonia source or keep just one or two fish in the tank to keep the biological filter going until you need the tank again in the future. That's how I would handle your situation.

Hope this helps.