Dead Angels

[F2FTech]

Problem: Of my 6 original Angels 5 have died overnight (one survives)

Background: I have been building up my tank over the past two years, slowly introducing fish. The last fish added was approx. 1 year ago. I purchased my six angels as young (so that this would reduce them being antagonistic to each other and to other fish). I was never able to sex them but there seem to be 5 smaller and one larger Angel after 2 years. All behaved properly with no one being dominant. They share a tank with a mixture of other peaceful fish. Then suddenly overnight all but the larger Angel have died. No other fish have died. The last water change was a week ago. I have had a couple of Tetra and one of my Labs die during the past year but this was months apart and seem to be one offs.

Tank size: 300L
pH: 7.5
ammonia: Nil
nitrite: Nil
nitrate: Nil
tank temp: 24c

Fish Symptoms (include full description including lesion, color, location, fish behavior): None (although one looks like its had a nibble but I'm putting this down to the other fish after the Angel died.

Volume and Frequency of water changes: 25%-30% every 4 weeks

Chemical Additives or Media in your tank: None

Tank inhabitants: Mix of Barbs, Swordfish, some Cichlids (Labidochromis/Lodotropheus), 1 Red Tailed Black Shark, 3 Pleco's, and some Tetra and of course 1x Angel

Recent additions to your tank (living or decoration): None - static for approx. 1 year

Exposure to chemicals: No - don't use.

Thanks for any help.

 

[fluttermoth]

Can I ask a couple more questions?

What test kits are you using? What are the levels of hardness and nitrate in your tap water?

 

[F2FTech]

Sure, Water Hardness is quite high at 109mg/l but Nitrate is quite low at 3ppl

 

[F2FTech]

Oh and I use the API 7 bottle test kits

 

[Byron]

When in an established aquarium with no recent introductions there are multiple fish deaths all at once, the water is the first thing to check, and it would seem that has been done with no obvious issues. Something toxic entering the tank is possible, but one would expect more than just one species to succumb. I will assume the heater and filter are OK.

So that leaves the fish themselves, and here I do see several problems.

Angelfish are sedate fish, and should not be combined with active fish like barbs. I don't know what species, and you mention "a mix," but while some are definitely worse than others in this situation, none are compatible.

Second problem is the Red Tailed Shark. This species is well known for becoming aggressive, and for reasons not known it frequently becomes intolerant of upper level fish with vertical patterns--like the angelfish (assuming they are the basic bar pattern variety).

Third, the cichlids Labidochromis and Iodotropheus are African rift lake species and these should never be combined with SA or Central American cichlids. They are worlds apart.

As for the other fish, I don't know the tetyra species, or the numbers, but these can turn very aggressive to sedate fish, though I would first suspect the afore-mentioned fish. Same goes for the swordtails, not very likely, but not a particularly good match regardless.

Now, before it is mentioned, I realize that these fish may have been together for months, but that is frankly irrelevant; fish have inherent behaviours and while some individuals may not show them or others might go over the top, there is always the possibility that at some point something environmental triggers the behaviour and trouble results. There are many, many threads on this forum about this happening out of the blue. If one spends time sitting quietly in front of an aquarium motionless--and I mean for over an hour without moving--the fish forget one is there and it is sometimes easier to see issues that would go unnoticed at feeding time or whenever. Something as "innocent" as one of the barbs swimming toward an angelfish and the angel turning away, with the two never getting even close, can spell trouble. Fish release pheromones and allomes that other fish read and these can be very stressful even if no physical interaction occurs. Until it does and it is then too late.

Something else in general, the water changes are too infrequent. Water changes should be every week, and the volume can vary but more is always better than less, and as you have too many fish that are not compatible in a fairly small space (to the fish, believe me, this is a very small space considering the species) 50-60% weekly would benefit. I'm not suggesting this is the issue, though it is a factor as all fish are impacted by water quality.

Byron.

 

[F2FTech]

I have a larger than needed filter and check the water regularly - I know this is no substitute but weekly changes are not practical. I have accepted advice from my local suppliers on the compatibility of the fish. Lessons learnt - do your own homework. I have (through trial and error) setup "zones" in the tank, using plants, to ensure that the fish have territories and have not seen any aggression from the red tail shark, but as you suggested I haven't spent hours monitoring him (if anything he prefers to keep himself to himself and hides away). I also change the zones every 3 months to help the fish (I read that this was important to ensure that the fish don't get territorial).

Thank you for your guidance. I will put the deaths down to experience and look to eventually have all the fish from the same geographical area.

 

[Byron]

Your response post caused me to re-read the thread (which I usually do in such cases) and I see I missed something previously, on the water hardness. Hoping it will help, I'll mention it.

A GH of 109 mg/l is soft, not hard. We tend to use one of two units in the hobby for GH and KH, ppm (parts per million) which is the same as mg/l, and degrees. A GH of 109 ppm equals 6 dGH, soft water. This is ideal for all fish mentioned except the rift lake cichlids which must have mineral in the water. Something to consider as you move forward.

You are quite correct that filtration cannot ever replace water changes, they achieve two different things. Advice from stores is often unfortunately misleading at best, and detrimental to the fish. Lesson learned, and one we have all learned believe me. I have been in this hobby for more than 20 years, and I am still learning.

Breaking up the sight lines can help in some situations. What is going on here is that the mix of non-compatible fish and too many in the space has caused the fish to be somewhat restrained, which may seem ironic. Stress, which I can guarantee is present, can increase aggression or retard it, but the latter is not a good thing because the effect on the fish is even worse. Dr. Loiselle's citation in my signature is apropos.

I hesitate to say the following, as you will assume I am harping on you, but I'm not, and others less experienced may read this thread and assume incorrectly if we don't set the record straight. Weekly partial water changes are a necessary part of this hobby for most circumstances if we want our fish to be healthy. I don't know why this isn't "practical" for you, and I am not asking for the reason, but it is certainly detrimental to your fish especially under the circumstances outlined. Something most of us on this forum care very deeply about is the welfare of fish. They may just be fish, but they are living creatures and if we are going to take the responsibility to have them, we should be prepared to look after them.

Byron.