[Lyn]

I have two tanks: a 65 and a 30 gallon, both heavily planted.

I do weekly 40% water changes and measure Ph, Ammonia, Nitrite, and Nitrate now and again. Sometimes the Ph fluctuates due to CO2 levels and sometimes I get a bit of Nitrate, but all the other readings are very stable and safe. I inject canister CO2 and have indicators showing me when adequate levels are reached. I used the same substrate for both tanks when setting them up: Seachem Flourite topped with gravel. I use Rena Filstar canister filters for both and excellent LED lighting for plants. They have both been set up and running well for 2 years.

I feed flakes, bottom wafers, and frozen blood worms and brine shrimp, alternating the food and only feeding every other day.

I have never had a problem with the 65 gallon, but recently (over the last 5 months or so) have had numerous bottom dwellers die. The first was a young albino bristlenose pleco. She lived for around 3 months and I could see no reason for her death. There is wood in the tank. Then the next were panda corys, aquatic frogs, then peppered corys.

I don't use antibiotics. I have been thinking of taking all the inhabitants and plants out and doing a thorough vacuum of the substrate in case of any pollution there. Another thing I just thought of as I am writing this is that because the problem tank is small, is it possible for the brine shrimp I am feeding to contribute too much salinity to the water and it has accumulated?

Any help would be most appreciated.

 

[Rjjm]

Unless you are over feeding them, there should not be any reason for them to die due to feeding them brine shrimp specially if you are changing the water on a weekly basis. The thing I wonder is your mixture of co2. Also, any rocks or wood present that is not bought from pet store? Another thing to is your temperature. Do you have heater and what is it set at? When you change your water, are you putting cycled water? The same temperature as your tank set up?

 

[VElderton]

You have been given a number of water parameters to consider ... all are possible issues. Any of them could point to an environmental source of contamination.

Have all the fish, other life and aquascaping in the tank remained the same in last 2 few months including the plants, rocks etc ... ? Any new additions are possible sources of introduced viruses or other infectious agents.

What is your source water? If you are on a central water source i.e city, municipal water that changes throughout the year ,.. it not constant. Various changes occur, levels of purification chemicals can change especially through the winter.

It's a complex ecological system we are dependant on as well as the life we maintain in our tanks; it changes and is dynamic and sometimes not all our fish in our closed systems can adapt.

 

[Lyn]

Thanks Rjjm.

The co2 is measured by a glass droplet-type thing where the inner bubble is the colour it should become if there is an adequate amount for the plants and the outer colour is a reactive that changes colour. I also measure the ph since that can drop with too much co2 in such a small tank. I have some rocks in there that I have used for a long time...like years but nothing else not sold commercially. The other tank where everyone is doing well has some wood from a lake.

I am fortunate to have well water that I don't have to treat. We do have a sterilizing UV lamp that the water goes through before coming into the house. I don't think that can be an issue since the other tank is fine. And yes, I use my hand to ensure the water is the same temp when I replace it. The heater almost seems redundant. We heat with wood and the tank sits at around 76-78 F. The heater is set for 71.

 

[Lyn]

Thanks VEI.

I think I answered your questions when I replied to RJJM. There have been no new additions except the corys who died.

It is truly puzzling!

 

[Mick2016]

"They have both been set up and running well for 2 years . . . I have been thinking of taking all the inhabitants and plants out and doing a thorough vacuum of the substrate in case of any pollution there."

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Agreed, Lyn. This is not likely anything to do with your maintenance routine, water parameters, and the like . . . OTHERWISE, both tanks would have dead bottom dwellers.

My hunch is that some foreign substance has got into the soil/gravel of the one tank. Since the middle and upper swimmers have not been affected, I would focus on the substrate. That is, if you have ruled out any defect or illness (or old age!) with the fish who have died.

My next step would be giving a deep - to the glass bottom - vacuum of the entire area covered by the substrate. Side to side; corner to corner. Repeat a couple of days later. (I wouldn't remove/rinse the substrate as you would have to start cycling the tank all over again. I would only do that as a last resort.) Wait a week. Then, buy a single (young) Cory - from a different supplier than the previous corys, pleco and frogs - and see if it survives.

 

[Lyn]

Thanks ****. I have done that, will repeat, and follow your advice. I really appreciate all the great input.

 

[Mick2016]

Glad to help.

BTW: I am NOT an expert at all. Just went with my gut and what I would do if I found myself in the same situation.

Keep us posted!

P.S. An alternative to buying any other bottom dwellers at this time would be to transfer one of your own - if you have one - from your other tank in a week's time. Of course, not a good idea if you are attached to that fish in any special way. In that case, go with getting a new Cory to which you have not yet become so attached.

(My apologies to any readers who may think this a cruel thing to do . . . BUT, after all, such a test is the ultimate proof that the substrate has improved if, in fact, it was the cause of death for the previous bottom-dwelling tenants in the first place.)

 

[Rjjm]

One advice to buying a new bottom dweller is make sure you buy from reputable pet store. Some pet stores have only one big filter system connected to their whole tanks. This means trouble to whoever is buying the fishes

 

[Mick2016]

On the other hand . . . fishes I have purchased that died within a couple days were bought from a store which had filtration systems on each individual tank. The fishes from the retailer with "one big filter system" have all acclimated to my aquarium as expected.

So . . . I don't think it matters so much WHAT system is used, but HOW well it is maintained - which, of course, depends upon the store's staff.