Help!!! Rasbora Hets are dying

PedrosPinnacle

I have a 75g freshwater aquarium. I have had 18 Rasbora Hets for about a month now. However three have died in the past three days. I observed one sinking to the bottom of the tank and then wildly swimming around before dying. I checked my water and here are the conditions:

Nitrates - 20 ppm
Nitrites - 0 ppm
Hardness - approx. 300 ppm
Chlorine 0 ppm
Alkalinity - approx. 90 ppm
PH - 8
Temp. - 78F

*Note: My water is very hard with a relatively high PH. However all of the fish were born locally in similar water conditions.

Tankmates - 7 Small Koi Angelfish, 6 Japonica Shrimp, 1 Bushy Nosed Plecco, 1 Flower Shrimp. (No one has been aggressive that I have observed).

I have two Marineland HOB filters.

Any ideas?

BettaKeeper

Did you see any physical signs of illness like ich? When you say one was wildly swimming about, was it rubbing against objects (parasites) ?

PedrosPinnacle

No physical signs of illness. No bulging eyes, no white spots. He wasn't rubbing against anything. He just started swimming violently in circles and then just stopped. Someone recommended I soak frozen food in garlic extract. I guess it's supposed to help flush out the digestive system including parasites and bacteria.

BettaKeeper

That's strange, never heard of the garlic thing either. Sorry but I don't know exactly how to help.

PedrosPinnacle

That's okay. It is definitely a mystery. I just hope I can find the cause before I lose them all.

BettaKeeper

Yes, good luck.