Fungal Infection

Ways to increase oxygen levels are by making sure the water is circulating well. This can be by making sure the filter outflow is moving the water along just under the surface or by using an airstone powered by an air pump (the bubbles churn the water up rather than oxygen dissolving from the bubbles).

Fungal infections often get in when the fish is stressed. Is this one being picked on; are the levels of ammonia and nitrite at zero? And are you sure it is fungus not a bacterial infection?

This is him as he was on Monday.  The redness around the edge has gone and the patch has gone down a bit.  We allowed him out earlier as he seemed a bit better, but was being bullied again, so we put him back in isolation in the main tank.

I've checked the levels.  Ammonia is on the lowest bit.  Nitrate is in the 12.5mg/l bit.  Nitrite is 0.3mg/l bit.  I've just done another partial water change.

We've lost a penguin tetra and the smaller Angel Fish is struggling - he's swimming upside down at the moment. :-(

The things you have to remove from the filter are those media which will remove the medication. Carbon will do this, as will zeolite. The sponges, ceramic media, filter wool etc will not remove the medication and can stay in the filter. The problems arise with those filters that have only carbon containing cartridges. If you remove them, you remove all the bacteria as well. If you are seeing raised levels of ammonia and nitrite, it suggests that you have removed a lot of your bacteria, and the raised levels are stressing the affected fish making it harder for it to recover.
Raised levels of ammonia and nitrite will cause the gulping at the surface you are seeing. Ammonia burns the fish's gills making it harder to absorb oxygen and nitrite binds to the red blood cells like carbon monoxide does to us. The fish feel as though they are suffocating and instinctively go to where the water is richer in oxygen, just under the surface.

Can you tell me exactly what is supposed to be inside your filter and what you have removed.

You need to keep those levels low and the only way is by water changes, I'm afraid. Because you are treating the fish, you will remove some med with every water change so you need to replace it. If it is a med that is dosed on certain days, add it after you've done a water change if the levels show one is needed (ie ammonia and/or nitrite above 0.25). On non-dose days, add the amount of med needed to treat the amount of new water you add.

At the moment, the water is your priority as the rest of the fish will be affected by that. The stress of having ammonia and nitrite in the water will make any sick fish worse.

As you kept the filter media in water the bacteria on there should still be alive though without food they may have started to go dormant. The good news is that they weren't out of the filter very long so if they have started to go dormant they'll wake up quickly.

It is possible that the stuff that looks like zeolite might actually be ceramic media. Zeolite is usually found in cartridges.
What is the make and model of the filter? I can see if I can find it, and what the media is.

Hagen have most of their manuals on-line - this is what I've found for the Fluval 305.

Looking at that manual, they say the bottom basket should contain prefilter, carbon or zeo-carb (a mixture of zeolite and carbon). This is what they mean by prefilter and this is zeo-carb. They also make something called ammonia remover which looks very similar to zeolite and is what you might have in your filter.

I do not like these ammonia removing media in filters. At the start, they remove the ammonia so that there is none left to stimulate bacterial growth. Then they get full and stop working and you don't have any bacteria to remove the ammonia so the level of that goes up in the tank. The good news is that yours will probably be full by now if you haven't changed them since you got the filter so they probably won't absorb ammonia or medication any more but will be a home for the filter bacteria which would have grown after the ammonia remover/zeolite got full.


Leave all the media in the filter for now. Hopefully the barb will recover, and treat if necessary with the media in there.



But long term I would think seriously about your media. I would change the bottom basket to that prefilter or maybe a coarse sponge, any make cut to fit the basket. In the top basket I would put a ceramic medium with a layer of filter wool on top, any make will do, this is Fluval's ceramic medium. You didn't mention what is in the middle basket, but the best would be more ceramic medium.
You would need to change the media a bit at a time. At the most, do one basket at a time with at least a month between changes - six to eight weeks would be better.

As I've mentioned, zeo-carb and ammonia remover are not a good idea as they starve the bacteria and are not as good a home for bacteria as sponges or ceramics. Carbon also gets full and stops working - but it's only uses are to remove the brown that comes out of wood and removing medication once treatment has finished - but you need new carbon for that. Carbon is a hangover from decades ago but it is cheap which is why filter manufacturers insist on using it.

Ceramic media starts to crumble when it needs replacing; it should last for years as for sponges. When It does start to go, only replace some of it in one go; maybe put the new stuff in a mesh bag to keep them separate till you've replaced all of it.


A lot of people don't like those media that remove nitrate and phosphate, especially those that have plants in the tank as plants do need nitrate and phosphate. But we have members (RichardW) who know a lot more about plants than me and may be able to comment further on this type of media. If you don't have live plants, I don't think it matters much, though they may influence algae growth.

Re your comment about the media that came with the tank - I have found there are people who prefer to take the chemical approach rather than the biological one!The problem with chemical media is that they get full and need replacing regularly. Biological methods are self replicating